;;; js.el --- Major mode for editing JavaScript  -*- lexical-binding: t -*-

;; Copyright (C) 2008-2017 Free Software Foundation, Inc.

;; Author: Karl Landstrom <karl.landstrom@brgeight.se>
;;         Daniel Colascione <dan.colascione@gmail.com>
;; Maintainer: Daniel Colascione <dan.colascione@gmail.com>
;; Version: 9
;; Date: 2009-07-25
;; Keywords: languages, javascript

;; This file is part of GNU Emacs.

;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary

;; This is based on Karl Landstrom's barebones javascript-mode. This
;; is much more robust and works with cc-mode's comment filling
;; (mostly).
;;
;; The main features of this JavaScript mode are syntactic
;; highlighting (enabled with `font-lock-mode' or
;; `global-font-lock-mode'), automatic indentation and filling of
;; comments, C preprocessor fontification, and MozRepl integration.
;;
;; General Remarks:
;;
;; XXX: This mode assumes that block comments are not nested inside block
;; XXX: comments
;;
;; Exported names start with "js-"; private names start with
;; "js--".

;;; Code:


(require 'cc-mode)
(require 'newcomment)
(require 'thingatpt)                    ; forward-symbol etc
(require 'imenu)
(require 'moz nil t)
(require 'json nil t)
(require 'sgml-mode)
(require 'prog-mode)

(eval-when-compile
  (require 'cl-lib)
  (require 'ido))

(defvar inferior-moz-buffer)
(defvar moz-repl-name)
(defvar ido-cur-list)
(defvar electric-layout-rules)
(declare-function ido-mode "ido" (&optional arg))
(declare-function inferior-moz-process "ext:mozrepl" ())

;;; Constants

(defconst js--name-start-re "[a-zA-Z_$]"
  "Regexp matching the start of a JavaScript identifier, without grouping.")

(defconst js--stmt-delim-chars "^;{}?:")

(defconst js--name-re (concat js--name-start-re
                              "\\(?:\\s_\\|\\sw\\)*")
  "Regexp matching a JavaScript identifier, without grouping.")

(defconst js--objfield-re (concat js--name-re ":")
  "Regexp matching the start of a JavaScript object field.")

(defconst js--dotted-name-re
  (concat js--name-re "\\(?:\\." js--name-re "\\)*")
  "Regexp matching a dot-separated sequence of JavaScript names.")

(defconst js--cpp-name-re js--name-re
  "Regexp matching a C preprocessor name.")

(defconst js--opt-cpp-start "^\\s-*#\\s-*\\([[:alnum:]]+\\)"
  "Regexp matching the prefix of a cpp directive.
This includes the directive name, or nil in languages without
preprocessor support.  The first submatch surrounds the directive
name.")

(defconst js--plain-method-re
  (concat "^\\s-*?\\(" js--dotted-name-re "\\)\\.prototype"
          "\\.\\(" js--name-re "\\)\\s-*?=\\s-*?\\(function\\)\\_>")
  "Regexp matching an explicit JavaScript prototype \"method\" declaration.
Group 1 is a (possibly-dotted) class name, group 2 is a method name,
and group 3 is the `function' keyword.")

(defconst js--plain-class-re
  (concat "^\\s-*\\(" js--dotted-name-re "\\)\\.prototype"
          "\\s-*=\\s-*{")
  "Regexp matching a JavaScript explicit prototype \"class\" declaration.
An example of this is \"Class.prototype = { method1: ...}\".")

;; var NewClass = BaseClass.extend(
(defconst js--mp-class-decl-re
  (concat "^\\s-*var\\s-+"
          "\\(" js--name-re "\\)"
          "\\s-*=\\s-*"
          "\\(" js--dotted-name-re
          "\\)\\.extend\\(?:Final\\)?\\s-*(\\s-*{?\\s-*$"))

;; var NewClass = Class.create()
(defconst js--prototype-obsolete-class-decl-re
  (concat "^\\s-*\\(?:var\\s-+\\)?"
          "\\(" js--dotted-name-re "\\)"
          "\\s-*=\\s-*Class\\.create()"))

(defconst js--prototype-objextend-class-decl-re-1
  (concat "^\\s-*Object\\.extend\\s-*("
          "\\(" js--dotted-name-re "\\)"
          "\\s-*,\\s-*{"))

(defconst js--prototype-objextend-class-decl-re-2
  (concat "^\\s-*\\(?:var\\s-+\\)?"
          "\\(" js--dotted-name-re "\\)"
          "\\s-*=\\s-*Object\\.extend\\s-*("))

;; var NewClass = Class.create({
(defconst js--prototype-class-decl-re
  (concat "^\\s-*\\(?:var\\s-+\\)?"
          "\\(" js--name-re "\\)"
          "\\s-*=\\s-*Class\\.create\\s-*(\\s-*"
          "\\(?:\\(" js--dotted-name-re "\\)\\s-*,\\s-*\\)?{?"))

;; Parent class name(s) (yes, multiple inheritance in JavaScript) are
;; matched with dedicated font-lock matchers
(defconst js--dojo-class-decl-re
  (concat "^\\s-*dojo\\.declare\\s-*(\"\\(" js--dotted-name-re "\\)"))

(defconst js--extjs-class-decl-re-1
  (concat "^\\s-*Ext\\.extend\\s-*("
          "\\s-*\\(" js--dotted-name-re "\\)"
          "\\s-*,\\s-*\\(" js--dotted-name-re "\\)")
  "Regexp matching an ExtJS class declaration (style 1).")

(defconst js--extjs-class-decl-re-2
  (concat "^\\s-*\\(?:var\\s-+\\)?"
          "\\(" js--name-re "\\)"
          "\\s-*=\\s-*Ext\\.extend\\s-*(\\s-*"
          "\\(" js--dotted-name-re "\\)")
  "Regexp matching an ExtJS class declaration (style 2).")

(defconst js--mochikit-class-re
  (concat "^\\s-*MochiKit\\.Base\\.update\\s-*(\\s-*"
          "\\(" js--dotted-name-re "\\)")
  "Regexp matching a MochiKit class declaration.")

(defconst js--dummy-class-style
  '(:name "[Automatically Generated Class]"))

(defconst js--class-styles
  `((:name            "Plain"
     :class-decl      ,js--plain-class-re
     :prototype       t
     :contexts        (toplevel)
     :framework       javascript)

    (:name            "MochiKit"
     :class-decl      ,js--mochikit-class-re
     :prototype       t
     :contexts        (toplevel)
     :framework       mochikit)

    (:name            "Prototype (Obsolete)"
     :class-decl      ,js--prototype-obsolete-class-decl-re
     :contexts        (toplevel)
     :framework       prototype)

    (:name            "Prototype (Modern)"
     :class-decl      ,js--prototype-class-decl-re
     :contexts        (toplevel)
     :framework       prototype)

    (:name            "Prototype (Object.extend)"
     :class-decl      ,js--prototype-objextend-class-decl-re-1
     :prototype       t
     :contexts        (toplevel)
     :framework       prototype)

    (:name            "Prototype (Object.extend) 2"
     :class-decl      ,js--prototype-objextend-class-decl-re-2
     :prototype       t
     :contexts        (toplevel)
     :framework       prototype)

    (:name            "Dojo"
     :class-decl      ,js--dojo-class-decl-re
     :contexts        (toplevel)
     :framework       dojo)

    (:name            "ExtJS (style 1)"
     :class-decl      ,js--extjs-class-decl-re-1
     :prototype       t
     :contexts        (toplevel)
     :framework       extjs)

    (:name            "ExtJS (style 2)"
     :class-decl      ,js--extjs-class-decl-re-2
     :contexts        (toplevel)
     :framework       extjs)

    (:name            "Merrill Press"
     :class-decl      ,js--mp-class-decl-re
     :contexts        (toplevel)
     :framework       merrillpress))

  "List of JavaScript class definition styles.

A class definition style is a plist with the following keys:

:name is a human-readable name of the class type

:class-decl is a regular expression giving the start of the
class.  Its first group must match the name of its class.  If there
is a parent class, the second group should match, and it should be
the name of the class.

If :prototype is present and non-nil, the parser will merge
declarations for this constructs with others at the same lexical
level that have the same name.  Otherwise, multiple definitions
will create multiple top-level entries.  Don't use :prototype
unnecessarily: it has an associated cost in performance.

If :strip-prototype is present and non-nil, then if the class
name as matched contains
")

(defconst js--available-frameworks
  (cl-loop for style in js--class-styles
           for framework = (plist-get style :framework)
           unless (memq framework available-frameworks)
           collect framework into available-frameworks
           finally return available-frameworks)
  "List of available JavaScript frameworks symbols.")

(defconst js--function-heading-1-re
  (concat
   "^\\s-*function\\(?:\\s-\\|\\*\\)+\\(" js--name-re "\\)")
  "Regexp matching the start of a JavaScript function header.
Match group 1 is the name of the function.")

(defconst js--function-heading-2-re
  (concat
   "^\\s-*\\(" js--name-re "\\)\\s-*:\\s-*function\\_>")
  "Regexp matching the start of a function entry in an associative array.
Match group 1 is the name of the function.")

(defconst js--function-heading-3-re
  (concat
   "^\\s-*\\(?:var\\s-+\\)?\\(" js--dotted-name-re "\\)"
   "\\s-*=\\s-*function\\_>")
  "Regexp matching a line in the JavaScript form \"var MUMBLE = function\".
Match group 1 is MUMBLE.")

(defconst js--macro-decl-re
  (concat "^\\s-*#\\s-*define\\s-+\\(" js--cpp-name-re "\\)\\s-*(")
  "Regexp matching a CPP macro definition, up to the opening parenthesis.
Match group 1 is the name of the macro.")

(defun js--regexp-opt-symbol (list)
  "Like `regexp-opt', but surround the result with `\\\\_<' and `\\\\_>'."
  (concat "\\_<" (regexp-opt list t) "\\_>"))

(defconst js--keyword-re
  (js--regexp-opt-symbol
   '("abstract" "break" "case" "catch" "class" "const"
     "continue" "debugger" "default" "delete" "do" "else"
     "enum" "export" "extends" "final" "finally" "for"
     "function" "goto" "if" "implements" "import" "in"
     "instanceof" "interface" "native" "new" "package"
     "private" "protected" "public" "return" "static"
     "super" "switch" "synchronized" "throw"
     "throws" "transient" "try" "typeof" "var" "void" "let"
     "yield" "volatile" "while" "with"))
  "Regexp matching any JavaScript keyword.")

(defconst js--basic-type-re
  (js--regexp-opt-symbol
   '("boolean" "byte" "char" "double" "float" "int" "long"
     "short" "void"))
  "Regular expression matching any predefined type in JavaScript.")

(defconst js--constant-re
  (js--regexp-opt-symbol '("false" "null" "undefined"
                                 "Infinity" "NaN"
                                 "true" "arguments" "this"))
  "Regular expression matching any future reserved words in JavaScript.")


(defconst js--font-lock-keywords-1
  (list
   "\\_<import\\_>"
   (list js--function-heading-1-re 1 font-lock-function-name-face)
   (list js--function-heading-2-re 1 font-lock-function-name-face))
  "Level one font lock keywords for `js-mode'.")

(defconst js--font-lock-keywords-2
  (append js--font-lock-keywords-1
          (list (list js--keyword-re 1 font-lock-keyword-face)
                (list "\\_<for\\_>"
                      "\\s-+\\(each\\)\\_>" nil nil
                      (list 1 'font-lock-keyword-face))
                (cons js--basic-type-re font-lock-type-face)
                (cons js--constant-re font-lock-constant-face)))
  "Level two font lock keywords for `js-mode'.")

;; js--pitem is the basic building block of the lexical
;; database. When one refers to a real part of the buffer, the region
;; of text to which it refers is split into a conceptual header and
;; body. Consider the (very short) block described by a hypothetical
;; js--pitem:
;;
;;   function foo(a,b,c) { return 42; }
;;   ^                    ^            ^
;;   |                    |            |
;;   +- h-begin           +- h-end     +- b-end
;;
;; (Remember that these are buffer positions, and therefore point
;; between characters, not at them. An arrow drawn to a character
;; indicates the corresponding position is between that character and
;; the one immediately preceding it.)
;;
;; The header is the region of text [h-begin, h-end], and is
;; the text needed to unambiguously recognize the start of the
;; construct. If the entire header is not present, the construct is
;; not recognized at all. No other pitems may be nested inside the
;; header.
;;
;; The body is the region [h-end, b-end]. It may contain nested
;; js--pitem instances. The body of a pitem may be empty: in
;; that case, b-end is equal to header-end.
;;
;; The three points obey the following relationship:
;;
;;   h-begin < h-end <= b-end
;;
;; We put a text property in the buffer on the character *before*
;; h-end, and if we see it, on the character *before* b-end.
;;
;; The text property for h-end, js--pstate, is actually a list
;; of all js--pitem instances open after the marked character.
;;
;; The text property for b-end, js--pend, is simply the
;; js--pitem that ends after the marked character. (Because
;; pitems always end when the paren-depth drops below a critical
;; value, and because we can only drop one level per character, only
;; one pitem may end at a given character.)
;;
;; In the structure below, we only store h-begin and (sometimes)
;; b-end. We can trivially and quickly find h-end by going to h-begin
;; and searching for an js--pstate text property. Since no other
;; js--pitem instances can be nested inside the header of a
;; pitem, the location after the character with this text property
;; must be h-end.
;;
;; js--pitem instances are never modified (with the exception
;; of the b-end field). Instead, modified copies are added at
;; subsequence parse points.
;; (The exception for b-end and its caveats is described below.)
;;

(cl-defstruct (js--pitem (:type list))
  ;; IMPORTANT: Do not alter the position of fields within the list.
  ;; Various bits of code depend on their positions, particularly
  ;; anything that manipulates the list of children.

  ;; List of children inside this pitem's body
  (children nil :read-only t)

  ;; When we reach this paren depth after h-end, the pitem ends
  (paren-depth nil :read-only t)

  ;; Symbol or class-style plist if this is a class
  (type nil :read-only t)

  ;; See above
  (h-begin nil :read-only t)

  ;; List of strings giving the parts of the name of this pitem (e.g.,
  ;; '("MyClass" "myMethod"), or t if this pitem is anonymous
  (name nil :read-only t)

  ;; THIS FIELD IS MUTATED, and its value is shared by all copies of
  ;; this pitem: when we copy-and-modify pitem instances, we share
  ;; their tail structures, so all the copies actually have the same
  ;; terminating cons cell. We modify that shared cons cell directly.
  ;;
  ;; The field value is either a number (buffer location) or nil if
  ;; unknown.
  ;;
  ;; If the field's value is greater than `js--cache-end', the
  ;; value is stale and must be treated as if it were nil. Conversely,
  ;; if this field is nil, it is guaranteed that this pitem is open up
  ;; to at least `js--cache-end'. (This property is handy when
  ;; computing whether we're inside a given pitem.)
  ;;
  (b-end nil))

;; The pitem we start parsing with.
(defconst js--initial-pitem
  (make-js--pitem
   :paren-depth most-negative-fixnum
   :type 'toplevel))

;;; User Customization

(defgroup js nil
  "Customization variables for JavaScript mode."
  :tag "JavaScript"
  :group 'languages)

(defcustom js-indent-level 4
  "Number of spaces for each indentation step in `js-mode'."
  :type 'integer
  :safe 'integerp
  :group 'js)

(defcustom js-expr-indent-offset 0
  "Number of additional spaces for indenting continued expressions.
The value must be no less than minus `js-indent-level'."
  :type 'integer
  :safe 'integerp
  :group 'js)

(defcustom js-paren-indent-offset 0
  "Number of additional spaces for indenting expressions in parentheses.
The value must be no less than minus `js-indent-level'."
  :type 'integer
  :safe 'integerp
  :group 'js
  :version "24.1")

(defcustom js-square-indent-offset 0
  "Number of additional spaces for indenting expressions in square braces.
The value must be no less than minus `js-indent-level'."
  :type 'integer
  :safe 'integerp
  :group 'js
  :version "24.1")

(defcustom js-curly-indent-offset 0
  "Number of additional spaces for indenting expressions in curly braces.
The value must be no less than minus `js-indent-level'."
  :type 'integer
  :safe 'integerp
  :group 'js
  :version "24.1")

(defcustom js-switch-indent-offset 0
  "Number of additional spaces for indenting the contents of a switch block.
The value must not be negative."
  :type 'integer
  :safe 'integerp
  :group 'js
  :version "24.4")

(defcustom js-flat-functions nil
  "Treat nested functions as top-level functions in `js-mode'.
This applies to function movement, marking, and so on."
  :type 'boolean
  :group 'js)

(defcustom js-comment-lineup-func #'c-lineup-C-comments
  "Lineup function for `cc-mode-style', for C comments in `js-mode'."
  :type 'function
  :group 'js)

(defcustom js-enabled-frameworks js--available-frameworks
  "Frameworks recognized by `js-mode'.
To improve performance, you may turn off some frameworks you
seldom use, either globally or on a per-buffer basis."
  :type (cons 'set (mapcar (lambda (x)
                             (list 'const x))
                           js--available-frameworks))
  :group 'js)

(defcustom js-js-switch-tabs
  (and (memq system-type '(darwin)) t)
  "Whether `js-mode' should display tabs while selecting them.
This is useful only if the windowing system has a good mechanism
for preventing Firefox from stealing the keyboard focus."
  :type 'boolean
  :group 'js)

(defcustom js-js-tmpdir
  "~/.emacs.d/js/js"
  "Temporary directory used by `js-mode' to communicate with Mozilla.
This directory must be readable and writable by both Mozilla and Emacs."
  :type 'directory
  :group 'js)

(defcustom js-js-timeout 5
  "Reply timeout for executing commands in Mozilla via `js-mode'.
The value is given in seconds.  Increase this value if you are
getting timeout messages."
  :type 'integer
  :group 'js)

(defcustom js-indent-first-init nil
  "Non-nil means specially indent the first variable declaration's initializer.
Normally, the first declaration's initializer is unindented, and
subsequent declarations have their identifiers aligned with it:

  var o = {
      foo: 3
  };

  var o = {
      foo: 3
  },
      bar = 2;

If this option has the value t, indent the first declaration's
initializer by an additional level:

  var o = {
          foo: 3
      };

  var o = {
          foo: 3
      },
      bar = 2;

If this option has the value `dynamic', if there is only one declaration,
don't indent the first one's initializer; otherwise, indent it.

  var o = {
      foo: 3
  };

  var o = {
          foo: 3
      },
      bar = 2;"
  :version "25.1"
  :type '(choice (const nil) (const t) (const dynamic))
  :safe 'symbolp
  :group 'js)

(defcustom js-chain-indent nil
  "Use \"chained\" indentation.
Chained indentation applies when the current line starts with \".\".
If the previous expression also contains a \".\" at the same level,
then the \".\"s will be lined up:

  let x = svg.mumble()
             .chained;
"
  :version "26.1"
  :type 'boolean
  :safe 'booleanp
  :group 'js)

;;; KeyMap

(defvar js-mode-map
  (let ((keymap (make-sparse-keymap)))
    (define-key keymap [(control ?c) (meta ?:)] #'js-eval)
    (define-key keymap [(control ?c) (control ?j)] #'js-set-js-context)
    (define-key keymap [(control meta ?x)] #'js-eval-defun)
    (define-key keymap [(meta ?.)] #'js-find-symbol)
    (easy-menu-define nil keymap "JavaScript Menu"
      '("JavaScript"
        ["Select New Mozilla Context..." js-set-js-context
         (fboundp #'inferior-moz-process)]
        ["Evaluate Expression in Mozilla Context..." js-eval
         (fboundp #'inferior-moz-process)]
        ["Send Current Function to Mozilla..." js-eval-defun
         (fboundp #'inferior-moz-process)]))
    keymap)
  "Keymap for `js-mode'.")

;;; Syntax table and parsing

(defvar js-mode-syntax-table
  (let ((table (make-syntax-table)))
    (c-populate-syntax-table table)
    (modify-syntax-entry ?$ "_" table)
    (modify-syntax-entry ?` "\"" table)
    table)
  "Syntax table for `js-mode'.")

(defvar js--quick-match-re nil
  "Autogenerated regexp used by `js-mode' to match buffer constructs.")

(defvar js--quick-match-re-func nil
  "Autogenerated regexp used by `js-mode' to match constructs and functions.")

(make-variable-buffer-local 'js--quick-match-re)
(make-variable-buffer-local 'js--quick-match-re-func)

(defvar js--cache-end 1
  "Last valid buffer position for the `js-mode' function cache.")
(make-variable-buffer-local 'js--cache-end)

(defvar js--last-parse-pos nil
  "Latest parse position reached by `js--ensure-cache'.")
(make-variable-buffer-local 'js--last-parse-pos)

(defvar js--state-at-last-parse-pos nil
  "Parse state at `js--last-parse-pos'.")
(make-variable-buffer-local 'js--state-at-last-parse-pos)

(defun js--flatten-list (list)
  (cl-loop for item in list
           nconc (cond ((consp item)
                        (js--flatten-list item))
                       (item (list item)))))

(defun js--maybe-join (prefix separator suffix &rest list)
  "Helper function for `js--update-quick-match-re'.
If LIST contains any element that is not nil, return its non-nil
elements, separated by SEPARATOR, prefixed by PREFIX, and ended
with SUFFIX as with `concat'.  Otherwise, if LIST is empty, return
nil.  If any element in LIST is itself a list, flatten that
element."
  (setq list (js--flatten-list list))
  (when list
    (concat prefix (mapconcat #'identity list separator) suffix)))

(defun js--update-quick-match-re ()
  "Internal function used by `js-mode' for caching buffer constructs.
This updates `js--quick-match-re', based on the current set of
enabled frameworks."
  (setq js--quick-match-re
        (js--maybe-join
         "^[ \t]*\\(?:" "\\|" "\\)"

         ;; #define mumble
         "#define[ \t]+[a-zA-Z_]"

         (when (memq 'extjs js-enabled-frameworks)
           "Ext\\.extend")

         (when (memq 'prototype js-enabled-frameworks)
           "Object\\.extend")

          ;; var mumble = THING (
         (js--maybe-join
          "\\(?:var[ \t]+\\)?[a-zA-Z_$0-9.]+[ \t]*=[ \t]*\\(?:"
          "\\|"
          "\\)[ \t]*("

          (when (memq 'prototype js-enabled-frameworks)
                    "Class\\.create")

          (when (memq 'extjs js-enabled-frameworks)
            "Ext\\.extend")

          (when (memq 'merrillpress js-enabled-frameworks)
            "[a-zA-Z_$0-9]+\\.extend\\(?:Final\\)?"))

         (when (memq 'dojo js-enabled-frameworks)
           "dojo\\.declare[ \t]*(")

         (when (memq 'mochikit js-enabled-frameworks)
           "MochiKit\\.Base\\.update[ \t]*(")

         ;; mumble.prototypeTHING
         (js--maybe-join
          "[a-zA-Z_$0-9.]+\\.prototype\\(?:" "\\|" "\\)"

          (when (memq 'javascript js-enabled-frameworks)
            '( ;; foo.prototype.bar = function(
              "\\.[a-zA-Z_$0-9]+[ \t]*=[ \t]*function[ \t]*("

              ;; mumble.prototype = {
              "[ \t]*=[ \t]*{")))))

  (setq js--quick-match-re-func
        (concat "function\\|" js--quick-match-re)))

(defun js--forward-text-property (propname)
  "Move over the next value of PROPNAME in the buffer.
If found, return that value and leave point after the character
having that value; otherwise, return nil and leave point at EOB."
  (let ((next-value (get-text-property (point) propname)))
    (if next-value
        (forward-char)

      (goto-char (next-single-property-change
                  (point) propname nil (point-max)))
      (unless (eobp)
        (setq next-value (get-text-property (point) propname))
        (forward-char)))

    next-value))

(defun js--backward-text-property (propname)
  "Move over the previous value of PROPNAME in the buffer.
If found, return that value and leave point just before the
character that has that value, otherwise return nil and leave
point at BOB."
    (unless (bobp)
      (let ((prev-value (get-text-property (1- (point)) propname)))
        (if prev-value
            (backward-char)

          (goto-char (previous-single-property-change
                      (point) propname nil (point-min)))

          (unless (bobp)
            (backward-char)
            (setq prev-value (get-text-property (point) propname))))

        prev-value)))

(defsubst js--forward-pstate ()
  (js--forward-text-property 'js--pstate))

(defsubst js--backward-pstate ()
  (js--backward-text-property 'js--pstate))

(defun js--pitem-goto-h-end (pitem)
  (goto-char (js--pitem-h-begin pitem))
  (js--forward-pstate))

(defun js--re-search-forward-inner (regexp &optional bound count)
  "Helper function for `js--re-search-forward'."
  (let ((parse)
        str-terminator
        (orig-macro-end (save-excursion
                          (when (js--beginning-of-macro)
                            (c-end-of-macro)
                            (point)))))
    (while (> count 0)
      (re-search-forward regexp bound)
      (setq parse (syntax-ppss))
      (cond ((setq str-terminator (nth 3 parse))
             (when (eq str-terminator t)
               (setq str-terminator ?/))
             (re-search-forward
              (concat "\\([^\\]\\|^\\)" (string str-terminator))
              (point-at-eol) t))
            ((nth 7 parse)
             (forward-line))
            ((or (nth 4 parse)
                 (and (eq (char-before) ?\/) (eq (char-after) ?\*)))
             (re-search-forward "\\*/"))
            ((and (not (and orig-macro-end
                            (<= (point) orig-macro-end)))
                  (js--beginning-of-macro))
             (c-end-of-macro))
            (t
             (setq count (1- count))))))
  (point))


(defun js--re-search-forward (regexp &optional bound noerror count)
  "Search forward, ignoring strings, cpp macros, and comments.
This function invokes `re-search-forward', but treats the buffer
as if strings, cpp macros, and comments have been removed.

If invoked while inside a macro, it treats the contents of the
macro as normal text."
  (unless count (setq count 1))
  (let ((saved-point (point))
        (search-fun
         (cond ((< count 0) (setq count (- count))
                #'js--re-search-backward-inner)
               ((> count 0) #'js--re-search-forward-inner)
               (t #'ignore))))
    (condition-case err
        (funcall search-fun regexp bound count)
      (search-failed
       (goto-char saved-point)
       (unless noerror
         (signal (car err) (cdr err)))))))


(defun js--re-search-backward-inner (regexp &optional bound count)
  "Auxiliary function for `js--re-search-backward'."
  (let ((parse)
        str-terminator
        (orig-macro-start
         (save-excursion
           (and (js--beginning-of-macro)
                (point)))))
    (while (> count 0)
      (re-search-backward regexp bound)
      (when (and (> (point) (point-min))
                 (save-excursion (backward-char) (looking-at "/[/*]")))
        (forward-char))
      (setq parse (syntax-ppss))
      (cond ((setq str-terminator (nth 3 parse))
             (when (eq str-terminator t)
               (setq str-terminator ?/))
             (re-search-backward
              (concat "\\([^\\]\\|^\\)" (string str-terminator))
              (point-at-bol) t))
            ((nth 7 parse)
             (goto-char (nth 8 parse)))
            ((or (nth 4 parse)
                 (and (eq (char-before) ?/) (eq (char-after) ?*)))
             (re-search-backward "/\\*"))
            ((and (not (and orig-macro-start
                            (>= (point) orig-macro-start)))
                  (js--beginning-of-macro)))
            (t
             (setq count (1- count))))))
  (point))


(defun js--re-search-backward (regexp &optional bound noerror count)
  "Search backward, ignoring strings, preprocessor macros, and comments.

This function invokes `re-search-backward' but treats the buffer
as if strings, preprocessor macros, and comments have been
removed.

If invoked while inside a macro, treat the macro as normal text."
  (js--re-search-forward regexp bound noerror (if count (- count) -1)))

(defun js--forward-expression ()
  "Move forward over a whole JavaScript expression.
This function doesn't move over expressions continued across
lines."
  (cl-loop
   ;; non-continued case; simplistic, but good enough?
   do (cl-loop until (or (eolp)
                         (progn
                           (forward-comment most-positive-fixnum)
                           (memq (char-after) '(?\, ?\; ?\] ?\) ?\}))))
               do (forward-sexp))

   while (and (eq (char-after) ?\n)
              (save-excursion
                (forward-char)
                (js--continued-expression-p)))))

(defun js--forward-function-decl ()
  "Move forward over a JavaScript function declaration.
This puts point at the `function' keyword.

If this is a syntactically-correct non-expression function,
return the name of the function, or t if the name could not be
determined.  Otherwise, return nil."
  (cl-assert (looking-at "\\_<function\\_>"))
  (let ((name t))
    (forward-word-strictly)
    (forward-comment most-positive-fixnum)
    (when (eq (char-after) ?*)
      (forward-char)
      (forward-comment most-positive-fixnum))
    (when (looking-at js--name-re)
      (setq name (match-string-no-properties 0))
      (goto-char (match-end 0)))
    (forward-comment most-positive-fixnum)
    (and (eq (char-after) ?\( )
         (ignore-errors (forward-list) t)
         (progn (forward-comment most-positive-fixnum)
                (and (eq (char-after) ?{)
                     name)))))

(defun js--function-prologue-beginning (&optional pos)
  "Return the start of the JavaScript function prologue containing POS.
A function prologue is everything from start of the definition up
to and including the opening brace.  POS defaults to point.
If POS is not in a function prologue, return nil."
  (let (prologue-begin)
    (save-excursion
      (if pos
          (goto-char pos)
        (setq pos (point)))

      (when (save-excursion
              (forward-line 0)
              (or (looking-at js--function-heading-2-re)
                  (looking-at js--function-heading-3-re)))

        (setq prologue-begin (match-beginning 1))
        (when (<= prologue-begin pos)
          (goto-char (match-end 0))))

      (skip-syntax-backward "w_")
      (and (or (looking-at "\\_<function\\_>")
               (js--re-search-backward "\\_<function\\_>" nil t))

           (save-match-data (goto-char (match-beginning 0))
                            (js--forward-function-decl))

           (<= pos (point))
           (or prologue-begin (match-beginning 0))))))

(defun js--beginning-of-defun-raw ()
  "Helper function for `js-beginning-of-defun'.
Go to previous defun-beginning and return the parse state for it,
or nil if we went all the way back to bob and don't find
anything."
  (js--ensure-cache)
  (let (pstate)
    (while (and (setq pstate (js--backward-pstate))
                (not (eq 'function (js--pitem-type (car pstate))))))
    (and (not (bobp)) pstate)))

(defun js--pstate-is-toplevel-defun (pstate)
  "Helper function for `js--beginning-of-defun-nested'.
If PSTATE represents a non-empty top-level defun, return the
top-most pitem.  Otherwise, return nil."
  (cl-loop for pitem in pstate
           with func-depth = 0
           with func-pitem
           if (eq 'function (js--pitem-type pitem))
           do (cl-incf func-depth)
           and do (setq func-pitem pitem)
           finally return (if (eq func-depth 1) func-pitem)))

(defun js--beginning-of-defun-nested ()
  "Helper function for `js--beginning-of-defun'.
Return the pitem of the function we went to the beginning of."
  (or
   ;; Look for the smallest function that encloses point...
   (cl-loop for pitem in (js--parse-state-at-point)
            if (and (eq 'function (js--pitem-type pitem))
                    (js--inside-pitem-p pitem))
            do (goto-char (js--pitem-h-begin pitem))
            and return pitem)

   ;; ...and if that isn't found, look for the previous top-level
   ;; defun
   (cl-loop for pstate = (js--backward-pstate)
            while pstate
            if (js--pstate-is-toplevel-defun pstate)
            do (goto-char (js--pitem-h-begin it))
            and return it)))

(defun js--beginning-of-defun-flat ()
  "Helper function for `js-beginning-of-defun'."
  (let ((pstate (js--beginning-of-defun-raw)))
    (when pstate
      (goto-char (js--pitem-h-begin (car pstate))))))

(defun js-beginning-of-defun (&optional arg)
  "Value of `beginning-of-defun-function' for `js-mode'."
  (setq arg (or arg 1))
  (while (and (not (eobp)) (< arg 0))
    (cl-incf arg)
    (when (and (not js-flat-functions)
               (or (eq (js-syntactic-context) 'function)
                   (js--function-prologue-beginning)))
      (js-end-of-defun))

    (if (js--re-search-forward
         "\\_<function\\_>" nil t)
        (goto-char (js--function-prologue-beginning))
      (goto-char (point-max))))

  (while (> arg 0)
    (cl-decf arg)
    ;; If we're just past the end of a function, the user probably wants
    ;; to go to the beginning of *that* function
    (when (eq (char-before) ?})
      (backward-char))

    (let ((prologue-begin (js--function-prologue-beginning)))
      (cond ((and prologue-begin (< prologue-begin (point)))
             (goto-char prologue-begin))

            (js-flat-functions
             (js--beginning-of-defun-flat))
            (t
             (js--beginning-of-defun-nested))))))

(defun js--flush-caches (&optional beg ignored)
  "Flush the `js-mode' syntax cache after position BEG.
BEG defaults to `point-min', meaning to flush the entire cache."
  (interactive)
  (setq beg (or beg (save-restriction (widen) (point-min))))
  (setq js--cache-end (min js--cache-end beg)))

(defmacro js--debug (&rest _arguments)
  ;; `(message ,@arguments)
  )

(defun js--ensure-cache--pop-if-ended (open-items paren-depth)
  (let ((top-item (car open-items)))
    (when (<= paren-depth (js--pitem-paren-depth top-item))
      (cl-assert (not (get-text-property (1- (point)) 'js-pend)))
      (put-text-property (1- (point)) (point) 'js--pend top-item)
      (setf (js--pitem-b-end top-item) (point))
      (setq open-items
            ;; open-items must contain at least two items for this to
            ;; work, but because we push a dummy item to start with,
            ;; that assumption holds.
            (cons (js--pitem-add-child (cl-second open-items) top-item)
                  (cddr open-items)))))
  open-items)

(defmacro js--ensure-cache--update-parse ()
  "Helper function for `js--ensure-cache'.
Update parsing information up to point, referring to parse,
prev-parse-point, goal-point, and open-items bound lexically in
the body of `js--ensure-cache'."
  `(progn
     (setq goal-point (point))
     (goto-char prev-parse-point)
     (while (progn
              (setq open-items (js--ensure-cache--pop-if-ended
                                open-items (car parse)))
              ;; Make sure parse-partial-sexp doesn't stop because we *entered*
              ;; the given depth -- i.e., make sure we're deeper than the target
              ;; depth.
              (cl-assert (> (nth 0 parse)
                         (js--pitem-paren-depth (car open-items))))
              (setq parse (parse-partial-sexp
                           prev-parse-point goal-point
                           (js--pitem-paren-depth (car open-items))
                           nil parse))

;;              (let ((overlay (make-overlay prev-parse-point (point))))
;;                (overlay-put overlay 'face '(:background "red"))
;;                (unwind-protect
;;                     (progn
;;                       (js--debug "parsed: %S" parse)
;;                       (sit-for 1))
;;                  (delete-overlay overlay)))

              (setq prev-parse-point (point))
              (< (point) goal-point)))

     (setq open-items (js--ensure-cache--pop-if-ended
                       open-items (car parse)))))

(defun js--show-cache-at-point ()
  (interactive)
  (require 'pp)
  (let ((prop (get-text-property (point) 'js--pstate)))
    (with-output-to-temp-buffer "*Help*"
      (pp prop))))

(defun js--split-name (string)
  "Split a JavaScript name into its dot-separated parts.
This also removes any prototype parts from the split name
\(unless the name is just \"prototype\" to start with)."
  (let ((name (save-match-data
                (split-string string "\\." t))))
    (unless (and (= (length name) 1)
                 (equal (car name) "prototype"))

      (setq name (remove "prototype" name)))))

(defvar js--guess-function-name-start nil)

(defun js--guess-function-name (position)
  "Guess the name of the JavaScript function at POSITION.
POSITION should be just after the end of the word \"function\".
Return the name of the function, or nil if the name could not be
guessed.

This function clobbers match data.  If we find the preamble
begins earlier than expected while guessing the function name,
set `js--guess-function-name-start' to that position; otherwise,
set that variable to nil."
  (setq js--guess-function-name-start nil)
  (save-excursion
    (goto-char position)
    (forward-line 0)
    (cond
     ((looking-at js--function-heading-3-re)
      (and (eq (match-end 0) position)
           (setq js--guess-function-name-start (match-beginning 1))
           (match-string-no-properties 1)))

     ((looking-at js--function-heading-2-re)
      (and (eq (match-end 0) position)
           (setq js--guess-function-name-start (match-beginning 1))
           (match-string-no-properties 1))))))

(defun js--clear-stale-cache ()
  ;; Clear any endings that occur after point
  (let (end-prop)
    (save-excursion
      (while (setq end-prop (js--forward-text-property
                             'js--pend))
        (setf (js--pitem-b-end end-prop) nil))))

  ;; Remove any cache properties after this point
  (remove-text-properties (point) (point-max)
                          '(js--pstate t js--pend t)))

(defun js--ensure-cache (&optional limit)
  "Ensures brace cache is valid up to the character before LIMIT.
LIMIT defaults to point."
  (setq limit (or limit (point)))
  (when (< js--cache-end limit)

    (c-save-buffer-state
        (open-items
         parse
         prev-parse-point
         name
         case-fold-search
         filtered-class-styles
         goal-point)

      ;; Figure out which class styles we need to look for
      (setq filtered-class-styles
            (cl-loop for style in js--class-styles
                     if (memq (plist-get style :framework)
                              js-enabled-frameworks)
                     collect style))

      (save-excursion
        (save-restriction
          (widen)

          ;; Find last known good position
          (goto-char js--cache-end)
          (unless (bobp)
            (setq open-items (get-text-property
                              (1- (point)) 'js--pstate))

            (unless open-items
              (goto-char (previous-single-property-change
                          (point) 'js--pstate nil (point-min)))

              (unless (bobp)
                (setq open-items (get-text-property (1- (point))
                                                    'js--pstate))
                (cl-assert open-items))))

          (unless open-items
            ;; Make a placeholder for the top-level definition
            (setq open-items (list js--initial-pitem)))

          (setq parse (syntax-ppss))
          (setq prev-parse-point (point))

          (js--clear-stale-cache)

          (narrow-to-region (point-min) limit)

          (cl-loop while (re-search-forward js--quick-match-re-func nil t)
                   for orig-match-start = (goto-char (match-beginning 0))
                   for orig-match-end = (match-end 0)
                   do (js--ensure-cache--update-parse)
                   for orig-depth = (nth 0 parse)

                   ;; Each of these conditions should return non-nil if
                   ;; we should add a new item and leave point at the end
                   ;; of the new item's header (h-end in the
                   ;; js--pitem diagram). This point is the one
                   ;; after the last character we need to unambiguously
                   ;; detect this construct. If one of these evaluates to
                   ;; nil, the location of the point is ignored.
                   if (cond
                       ;; In comment or string
                       ((nth 8 parse) nil)

                       ;; Regular function declaration
                       ((and (looking-at "\\_<function\\_>")
                             (setq name (js--forward-function-decl)))

                        (when (eq name t)
                          (setq name (js--guess-function-name orig-match-end))
                          (if name
                              (when js--guess-function-name-start
                                (setq orig-match-start
                                      js--guess-function-name-start))

                            (setq name t)))

                        (cl-assert (eq (char-after) ?{))
                        (forward-char)
                        (make-js--pitem
                         :paren-depth orig-depth
                         :h-begin orig-match-start
                         :type 'function
                         :name (if (eq name t)
                                   name
                                 (js--split-name name))))

                       ;; Macro
                       ((looking-at js--macro-decl-re)

                        ;; Macros often contain unbalanced parentheses.
                        ;; Make sure that h-end is at the textual end of
                        ;; the macro no matter what the parenthesis say.
                        (c-end-of-macro)
                        (js--ensure-cache--update-parse)

                        (make-js--pitem
                         :paren-depth (nth 0 parse)
                         :h-begin orig-match-start
                         :type 'macro
                         :name (list (match-string-no-properties 1))))

                       ;; "Prototype function" declaration
                       ((looking-at js--plain-method-re)
                        (goto-char (match-beginning 3))
                        (when (save-match-data
                                (js--forward-function-decl))
                          (forward-char)
                          (make-js--pitem
                           :paren-depth orig-depth
                           :h-begin orig-match-start
                           :type 'function
                           :name (nconc (js--split-name
                                         (match-string-no-properties 1))
                                        (list (match-string-no-properties 2))))))

                       ;; Class definition
                       ((cl-loop
                         with syntactic-context =
                         (js--syntactic-context-from-pstate open-items)
                         for class-style in filtered-class-styles
                         if (and (memq syntactic-context
                                       (plist-get class-style :contexts))
                                 (looking-at (plist-get class-style
                                                        :class-decl)))
                         do (goto-char (match-end 0))
                         and return
                         (make-js--pitem
                          :paren-depth orig-depth
                          :h-begin orig-match-start
                          :type class-style
                          :name (js--split-name
                                 (match-string-no-properties 1))))))

                   do (js--ensure-cache--update-parse)
                   and do (push it open-items)
                   and do (put-text-property
                           (1- (point)) (point) 'js--pstate open-items)
                   else do (goto-char orig-match-end))

          (goto-char limit)
          (js--ensure-cache--update-parse)
          (setq js--cache-end limit)
          (setq js--last-parse-pos limit)
          (setq js--state-at-last-parse-pos open-items)
          )))))

(defun js--end-of-defun-flat ()
  "Helper function for `js-end-of-defun'."
  (cl-loop while (js--re-search-forward "}" nil t)
           do (js--ensure-cache)
           if (get-text-property (1- (point)) 'js--pend)
           if (eq 'function (js--pitem-type it))
           return t
           finally do (goto-char (point-max))))

(defun js--end-of-defun-nested ()
  "Helper function for `js-end-of-defun'."
  (message "test")
  (let* (pitem
         (this-end (save-excursion
                     (and (setq pitem (js--beginning-of-defun-nested))
                          (js--pitem-goto-h-end pitem)
                          (progn (backward-char)
                                 (forward-list)
                                 (point)))))
         found)

    (if (and this-end (< (point) this-end))
        ;; We're already inside a function; just go to its end.
        (goto-char this-end)

      ;; Otherwise, go to the end of the next function...
      (while (and (js--re-search-forward "\\_<function\\_>" nil t)
                  (not (setq found (progn
                                     (goto-char (match-beginning 0))
                                     (js--forward-function-decl))))))

      (if found (forward-list)
        ;; ... or eob.
        (goto-char (point-max))))))

(defun js-end-of-defun (&optional arg)
  "Value of `end-of-defun-function' for `js-mode'."
  (setq arg (or arg 1))
  (while (and (not (bobp)) (< arg 0))
    (cl-incf arg)
    (js-beginning-of-defun)
    (js-beginning-of-defun)
    (unless (bobp)
      (js-end-of-defun)))

  (while (> arg 0)
    (cl-decf arg)
    ;; look for function backward. if we're inside it, go to that
    ;; function's end. otherwise, search for the next function's end and
    ;; go there
    (if js-flat-functions
        (js--end-of-defun-flat)

      ;; if we're doing nested functions, see whether we're in the
      ;; prologue. If we are, go to the end of the function; otherwise,
      ;; call js--end-of-defun-nested to do the real work
      (let ((prologue-begin (js--function-prologue-beginning)))
        (cond ((and prologue-begin (<= prologue-begin (point)))
               (goto-char prologue-begin)
               (re-search-forward "\\_<function")
               (goto-char (match-beginning 0))
               (js--forward-function-decl)
               (forward-list))

              (t (js--end-of-defun-nested)))))))

(defun js--beginning-of-macro (&optional lim)
  (let ((here (point)))
    (save-restriction
      (if lim (narrow-to-region lim (point-max)))
      (beginning-of-line)
      (while (eq (char-before (1- (point))) ?\\)
        (forward-line -1))
      (back-to-indentation)
      (if (and (<= (point) here)
               (looking-at js--opt-cpp-start))
          t
        (goto-char here)
        nil))))

(defun js--backward-syntactic-ws (&optional lim)
  "Simple implementation of `c-backward-syntactic-ws' for `js-mode'."
  (save-restriction
    (when lim (narrow-to-region lim (point-max)))

    (let ((in-macro (save-excursion (js--beginning-of-macro)))
          (pos (point)))

      (while (progn (unless in-macro (js--beginning-of-macro))
                    (forward-comment most-negative-fixnum)
                    (/= (point)
                        (prog1
                            pos
                          (setq pos (point)))))))))

(defun js--forward-syntactic-ws (&optional lim)
  "Simple implementation of `c-forward-syntactic-ws' for `js-mode'."
  (save-restriction
    (when lim (narrow-to-region (point-min) lim))
    (let ((pos (point)))
      (while (progn
               (forward-comment most-positive-fixnum)
               (when (eq (char-after) ?#)
                 (c-end-of-macro))
               (/= (point)
                   (prog1
                       pos
                     (setq pos (point)))))))))

;; Like (up-list -1), but only considers lists that end nearby"
(defun js--up-nearby-list ()
  (save-restriction
    ;; Look at a very small region so our computation time doesn't
    ;; explode in pathological cases.
    (narrow-to-region (max (point-min) (- (point) 500)) (point))
    (up-list -1)))

(defun js--inside-param-list-p ()
  "Return non-nil if point is in a function parameter list."
  (ignore-errors
    (save-excursion
      (js--up-nearby-list)
      (and (looking-at "(")
           (progn (forward-symbol -1)
                  (or (looking-at "function")
                      (progn (forward-symbol -1)
                             (looking-at "function"))))))))

(defun js--inside-dojo-class-list-p ()
  "Return non-nil if point is in a Dojo multiple-inheritance class block."
  (ignore-errors
    (save-excursion
      (js--up-nearby-list)
      (let ((list-begin (point)))
        (forward-line 0)
        (and (looking-at js--dojo-class-decl-re)
             (goto-char (match-end 0))
             (looking-at "\"\\s-*,\\s-*\\[")
             (eq (match-end 0) (1+ list-begin)))))))

;;; Font Lock
(defun js--make-framework-matcher (framework &rest regexps)
  "Helper function for building `js--font-lock-keywords'.
Create a byte-compiled function for matching a concatenation of
REGEXPS, but only if FRAMEWORK is in `js-enabled-frameworks'."
  (setq regexps (apply #'concat regexps))
  (byte-compile
   `(lambda (limit)
      (when (memq (quote ,framework) js-enabled-frameworks)
        (re-search-forward ,regexps limit t)))))

(defvar js--tmp-location nil)
(make-variable-buffer-local 'js--tmp-location)

(defun js--forward-destructuring-spec (&optional func)
  "Move forward over a JavaScript destructuring spec.
If FUNC is supplied, call it with no arguments before every
variable name in the spec.  Return true if this was actually a
spec.  FUNC must preserve the match data."
  (pcase (char-after)
    (?\[
     (forward-char)
     (while
         (progn
           (forward-comment most-positive-fixnum)
           (cond ((memq (char-after) '(?\[ ?\{))
                  (js--forward-destructuring-spec func))

                 ((eq (char-after) ?,)
                  (forward-char)
                  t)

                 ((looking-at js--name-re)
                  (and func (funcall func))
                  (goto-char (match-end 0))
                  t))))
     (when (eq (char-after) ?\])
       (forward-char)
       t))

    (?\{
     (forward-char)
     (forward-comment most-positive-fixnum)
     (while
         (when (looking-at js--objfield-re)
           (goto-char (match-end 0))
           (forward-comment most-positive-fixnum)
           (and (cond ((memq (char-after) '(?\[ ?\{))
                       (js--forward-destructuring-spec func))
                      ((looking-at js--name-re)
                       (and func (funcall func))
                       (goto-char (match-end 0))
                       t))
                (progn (forward-comment most-positive-fixnum)
                       (when (eq (char-after) ?\,)
                         (forward-char)
                         (forward-comment most-positive-fixnum)
                         t)))))
     (when (eq (char-after) ?\})
       (forward-char)
       t))))

(defun js--variable-decl-matcher (limit)
  "Font-lock matcher for variable names in a variable declaration.
This is a cc-mode-style matcher that *always* fails, from the
point of view of font-lock.  It applies highlighting directly with
`font-lock-apply-highlight'."
  (condition-case nil
      (save-restriction
        (narrow-to-region (point-min) limit)

        (let ((first t))
          (forward-comment most-positive-fixnum)
          (while
              (and (or first
                       (when (eq (char-after) ?,)
                         (forward-char)
                         (forward-comment most-positive-fixnum)
                         t))
                   (cond ((looking-at js--name-re)
                          (font-lock-apply-highlight
                           '(0 font-lock-variable-name-face))
                          (goto-char (match-end 0)))

                         ((save-excursion
                            (js--forward-destructuring-spec))

                          (js--forward-destructuring-spec
                           (lambda ()
                             (font-lock-apply-highlight
                              '(0 font-lock-variable-name-face)))))))

            (forward-comment most-positive-fixnum)
            (when (eq (char-after) ?=)
              (forward-char)
              (js--forward-expression)
              (forward-comment most-positive-fixnum))

            (setq first nil))))

    ;; Conditions to handle
    (scan-error nil)
    (end-of-buffer nil))

  ;; Matcher always "fails"
  nil)

(defconst js--font-lock-keywords-3
  `(
    ;; This goes before keywords-2 so it gets used preferentially
    ;; instead of the keywords in keywords-2. Don't use override
    ;; because that will override syntactic fontification too, which
    ;; will fontify commented-out directives as if they weren't
    ;; commented out.
    ,@cpp-font-lock-keywords ; from font-lock.el

    ,@js--font-lock-keywords-2

    ("\\.\\(prototype\\)\\_>"
     (1 font-lock-constant-face))

    ;; Highlights class being declared, in parts
    (js--class-decl-matcher
     ,(concat "\\(" js--name-re "\\)\\(?:\\.\\|.*$\\)")
     (goto-char (match-beginning 1))
     nil
     (1 font-lock-type-face))

    ;; Highlights parent class, in parts, if available
    (js--class-decl-matcher
     ,(concat "\\(" js--name-re "\\)\\(?:\\.\\|.*$\\)")
     (if (match-beginning 2)
         (progn
           (setq js--tmp-location (match-end 2))
           (goto-char js--tmp-location)
           (insert "=")
           (goto-char (match-beginning 2)))
       (setq js--tmp-location nil)
       (goto-char (point-at-eol)))
     (when js--tmp-location
       (save-excursion
         (goto-char js--tmp-location)
         (delete-char 1)))
     (1 font-lock-type-face))

    ;; Highlights parent class
    (js--class-decl-matcher
     (2 font-lock-type-face nil t))

    ;; Dojo needs its own matcher to override the string highlighting
    (,(js--make-framework-matcher
       'dojo
       "^\\s-*dojo\\.declare\\s-*(\""
       "\\(" js--dotted-name-re "\\)"
       "\\(?:\"\\s-*,\\s-*\\(" js--dotted-name-re "\\)\\)?")
     (1 font-lock-type-face t)
     (2 font-lock-type-face nil t))

    ;; Match Dojo base classes. Of course Mojo has to be different
    ;; from everything else under the sun...
    (,(js--make-framework-matcher
       'dojo
       "^\\s-*dojo\\.declare\\s-*(\""
       "\\(" js--dotted-name-re "\\)\"\\s-*,\\s-*\\[")
     ,(concat "[[,]\\s-*\\(" js--dotted-name-re "\\)\\s-*"
              "\\(?:\\].*$\\)?")
     (backward-char)
     (end-of-line)
     (1 font-lock-type-face))

    ;; continued Dojo base-class list
    (,(js--make-framework-matcher
       'dojo
       "^\\s-*" js--dotted-name-re "\\s-*[],]")
     ,(concat "\\(" js--dotted-name-re "\\)"
              "\\s-*\\(?:\\].*$\\)?")
     (if (save-excursion (backward-char)
                         (js--inside-dojo-class-list-p))
         (forward-symbol -1)
       (end-of-line))
     (end-of-line)
     (1 font-lock-type-face))

    ;; variable declarations
    ,(list
      (concat "\\_<\\(const\\|var\\|let\\)\\_>\\|" js--basic-type-re)
      (list #'js--variable-decl-matcher nil nil nil))

    ;; class instantiation
    ,(list
      (concat "\\_<new\\_>\\s-+\\(" js--dotted-name-re "\\)")
      (list 1 'font-lock-type-face))

    ;; instanceof
    ,(list
      (concat "\\_<instanceof\\_>\\s-+\\(" js--dotted-name-re "\\)")
      (list 1 'font-lock-type-face))

    ;; formal parameters
    ,(list
      (concat
       "\\_<function\\_>\\(\\s-+" js--name-re "\\)?\\s-*(\\s-*"
       js--name-start-re)
      (list (concat "\\(" js--name-re "\\)\\(\\s-*).*\\)?")
            '(backward-char)
            '(end-of-line)
            '(1 font-lock-variable-name-face)))

    ;; continued formal parameter list
    ,(list
      (concat
       "^\\s-*" js--name-re "\\s-*[,)]")
      (list js--name-re
            '(if (save-excursion (backward-char)
                                 (js--inside-param-list-p))
                 (forward-symbol -1)
               (end-of-line))
            '(end-of-line)
            '(0 font-lock-variable-name-face))))
  "Level three font lock for `js-mode'.")

(defun js--inside-pitem-p (pitem)
  "Return whether point is inside the given pitem's header or body."
  (js--ensure-cache)
  (cl-assert (js--pitem-h-begin pitem))
  (cl-assert (js--pitem-paren-depth pitem))

  (and (> (point) (js--pitem-h-begin pitem))
       (or (null (js--pitem-b-end pitem))
           (> (js--pitem-b-end pitem) (point)))))

(defun js--parse-state-at-point ()
  "Parse the JavaScript program state at point.
Return a list of `js--pitem' instances that apply to point, most
specific first.  In the worst case, the current toplevel instance
will be returned."
  (save-excursion
    (save-restriction
      (widen)
      (js--ensure-cache)
      (let ((pstate (or (save-excursion
                          (js--backward-pstate))
                        (list js--initial-pitem))))

        ;; Loop until we either hit a pitem at BOB or pitem ends after
        ;; point (or at point if we're at eob)
        (cl-loop for pitem = (car pstate)
                 until (or (eq (js--pitem-type pitem)
                               'toplevel)
                           (js--inside-pitem-p pitem))
                 do (pop pstate))

        pstate))))

(defun js--syntactic-context-from-pstate (pstate)
  "Return the JavaScript syntactic context corresponding to PSTATE."
  (let ((type (js--pitem-type (car pstate))))
    (cond ((memq type '(function macro))
           type)
          ((consp type)
           'class)
          (t 'toplevel))))

(defun js-syntactic-context ()
  "Return the JavaScript syntactic context at point.
When called interactively, also display a message with that
context."
  (interactive)
  (let* ((syntactic-context (js--syntactic-context-from-pstate
                             (js--parse-state-at-point))))

    (when (called-interactively-p 'interactive)
      (message "Syntactic context: %s" syntactic-context))

    syntactic-context))

(defun js--class-decl-matcher (limit)
  "Font lock function used by `js-mode'.
This performs fontification according to `js--class-styles'."
  (cl-loop initially (js--ensure-cache limit)
           while (re-search-forward js--quick-match-re limit t)
           for orig-end = (match-end 0)
           do (goto-char (match-beginning 0))
           if (cl-loop for style in js--class-styles
                       for decl-re = (plist-get style :class-decl)
                       if (and (memq (plist-get style :framework)
                                     js-enabled-frameworks)
                               (memq (js-syntactic-context)
                                     (plist-get style :contexts))
                               decl-re
                               (looking-at decl-re))
                       do (goto-char (match-end 0))
                       and return t)
           return t
           else do (goto-char orig-end)))

(defconst js--font-lock-keywords
  '(js--font-lock-keywords-3 js--font-lock-keywords-1
                                   js--font-lock-keywords-2
                                   js--font-lock-keywords-3)
  "Font lock keywords for `js-mode'.  See `font-lock-keywords'.")

(defconst js--syntax-propertize-regexp-regexp
  (rx
   ;; Start of regexp.
   "/"
   (0+ (or
        ;; Match characters outside of a character class.
        (not (any ?\[ ?/ ?\\))
        ;; Match backslash quoted characters.
        (and "\\" not-newline)
        ;; Match character class.
        (and
         "["
         (0+ (or
              (not (any ?\] ?\\))
              (and "\\" not-newline)))
         "]")))
   (group "/"))
  "Regular expression matching a JavaScript regexp literal.")

(defun js-syntax-propertize-regexp (end)
  (let ((ppss (syntax-ppss)))
    (when (eq (nth 3 ppss) ?/)
      ;; A /.../ regexp.
      (goto-char (nth 8 ppss))
      (when (and (looking-at js--syntax-propertize-regexp-regexp)
                 ;; Don't touch text after END.
                 (<= (match-end 1) end))
        (put-text-property (match-beginning 1) (match-end 1)
                           'syntax-table (string-to-syntax "\"/"))
        (goto-char (match-end 0))))))

(defun js-syntax-propertize (start end)
  ;; JavaScript allows immediate regular expression objects, written /.../.
  (goto-char start)
  (js-syntax-propertize-regexp end)
  (funcall
   (syntax-propertize-rules
    ;; Distinguish /-division from /-regexp chars (and from /-comment-starter).
    ;; FIXME: Allow regexps after infix ops like + ...
    ;; https://developer.mozilla.org/en/JavaScript/Reference/Operators
    ;; We can probably just add +, -, <, >, %, ^, ~, ?, : at which
    ;; point I think only * and / would be missing which could also be added,
    ;; but need care to avoid affecting the // and */ comment markers.
    ("\\(?:^\\|[=([{,:;|&!]\\|\\_<return\\_>\\)\\(?:[ \t]\\)*\\(/\\)[^/*]"
     (1 (ignore
	 (forward-char -1)
         (when (or (not (memq (char-after (match-beginning 0)) '(?\s ?\t)))
                   ;; If the / is at the beginning of line, we have to check
                   ;; the end of the previous text.
                   (save-excursion
                     (goto-char (match-beginning 0))
                     (forward-comment (- (point)))
                     (memq (char-before)
                           (eval-when-compile (append "=({[,:;" '(nil))))))
           (put-text-property (match-beginning 1) (match-end 1)
                              'syntax-table (string-to-syntax "\"/"))
           (js-syntax-propertize-regexp end)))))
    ("\\`\\(#\\)!" (1 "< b")))
   (point) end))

(defconst js--prettify-symbols-alist
  '(("=>" . ?⇒)
    (">=" . ?≥)
    ("<=" . ?≤))
  "Alist of symbol prettifications for JavaScript.")

;;; Indentation

(defconst js--possibly-braceless-keyword-re
  (js--regexp-opt-symbol
   '("catch" "do" "else" "finally" "for" "if" "try" "while" "with"
     "each"))
  "Regexp matching keywords optionally followed by an opening brace.")

(defconst js--declaration-keyword-re
  (regexp-opt '("var" "let" "const") 'words)
  "Regular expression matching variable declaration keywords.")

(defconst js--indent-operator-re
  (concat "[-+*/%<>&^|?:.]\\([^-+*/.]\\|$\\)\\|!?=\\|"
          (js--regexp-opt-symbol '("in" "instanceof")))
  "Regexp matching operators that affect indentation of continued expressions.")

(defun js--looking-at-operator-p ()
  "Return non-nil if point is on a JavaScript operator, other than a comma."
  (save-match-data
    (and (looking-at js--indent-operator-re)
         (or (not (eq (char-after) ?:))
             (save-excursion
               (and (js--re-search-backward "[?:{]\\|\\_<case\\_>" nil t)
                    (eq (char-after) ??))))
         (not (and
               (eq (char-after) ?/)
               (save-excursion
                 (eq (nth 3 (syntax-ppss)) ?/))))
         (not (and
               (eq (char-after) ?*)
               ;; Generator method (possibly using computed property).
               (looking-at (concat "\\* *\\(?:\\[\\|" js--name-re " *(\\)"))
               (save-excursion
                 (js--backward-syntactic-ws)
                 ;; We might misindent some expressions that would
                 ;; return NaN anyway.  Shouldn't be a problem.
                 (memq (char-before) '(?, ?} ?{))))))))

(defun js--find-newline-backward ()
  "Move backward to the nearest newline that is not in a block comment."
  (let ((continue t)
        (result t))
    (while continue
      (setq continue nil)
      (if (search-backward "\n" nil t)
          (let ((parse (syntax-ppss)))
            ;; We match the end of a // comment but not a newline in a
            ;; block comment.
            (when (nth 4 parse)
              (goto-char (nth 8 parse))
              ;; If we saw a block comment, keep trying.
              (unless (nth 7 parse)
                (setq continue t))))
        (setq result nil)))
    result))

(defun js--continued-expression-p ()
  "Return non-nil if the current line continues an expression."
  (save-excursion
    (back-to-indentation)
    (if (js--looking-at-operator-p)
        (or (not (memq (char-after) '(?- ?+)))
            (progn
              (forward-comment (- (point)))
              (not (memq (char-before) '(?, ?\[ ?\()))))
      (and (js--find-newline-backward)
           (progn
             (skip-chars-backward " \t")
             (or (bobp) (backward-char))
             (and (> (point) (point-min))
                  (save-excursion (backward-char) (not (looking-at "[/*]/")))
                  (js--looking-at-operator-p)
                  (and (progn (backward-char)
                              (not (looking-at "+\\+\\|--\\|/[/*]"))))))))))

(defun js--skip-term-backward ()
  "Skip a term before point; return t if a term was skipped."
  (let ((term-skipped nil))
    ;; Skip backward over balanced parens.
    (let ((progress t))
      (while progress
        (setq progress nil)
        ;; First skip whitespace.
        (skip-syntax-backward " ")
        ;; Now if we're looking at closing paren, skip to the opener.
        ;; This doesn't strictly follow JS syntax, in that we might
        ;; skip something nonsensical like "()[]{}", but it is enough
        ;; if it works ok for valid input.
        (when (memq (char-before) '(?\] ?\) ?\}))
          (setq progress t term-skipped t)
          (backward-list))))
    ;; Maybe skip over a symbol.
    (let ((save-point (point)))
      (if (and (< (skip-syntax-backward "w_") 0)
                 (looking-at js--name-re))
          ;; Skipped.
          (progn
            (setq term-skipped t)
            (skip-syntax-backward " "))
        ;; Did not skip, so restore point.
        (goto-char save-point)))
    (when (and term-skipped (> (point) (point-min)))
      (backward-char)
      (eq (char-after) ?.))))

(defun js--skip-terms-backward ()
  "Skip any number of terms backward.
Move point to the earliest \".\" without changing paren levels.
Returns t if successful, nil if no term was found."
  (when (js--skip-term-backward)
    ;; Found at least one.
    (let ((last-point (point)))
      (while (js--skip-term-backward)
        (setq last-point (point)))
      (goto-char last-point)
      t)))

(defun js--chained-expression-p ()
  "A helper for js--proper-indentation that handles chained expressions.
A chained expression is when the current line starts with '.' and the
previous line also has a '.' expression.
This function returns the indentation for the current line if it is
a chained expression line; otherwise nil.
This should only be called while point is at the start of the line's content,
as determined by `back-to-indentation'."
  (when js-chain-indent
    (save-excursion
      (when (and (eq (char-after) ?.)
                 (js--continued-expression-p)
                 (js--find-newline-backward)
                 (js--skip-terms-backward))
        (current-column)))))

(defun js--end-of-do-while-loop-p ()
  "Return non-nil if point is on the \"while\" of a do-while statement.
Otherwise, return nil.  A braceless do-while statement spanning
several lines requires that the start of the loop is indented to
the same column as the current line."
  (interactive)
  (save-excursion
    (save-match-data
      (when (looking-at "\\s-*\\_<while\\_>")
	(if (save-excursion
	      (skip-chars-backward "[ \t\n]*}")
	      (looking-at "[ \t\n]*}"))
	    (save-excursion
	      (backward-list) (forward-symbol -1) (looking-at "\\_<do\\_>"))
	  (js--re-search-backward "\\_<do\\_>" (point-at-bol) t)
	  (or (looking-at "\\_<do\\_>")
	      (let ((saved-indent (current-indentation)))
		(while (and (js--re-search-backward "^\\s-*\\_<" nil t)
			    (/= (current-indentation) saved-indent)))
		(and (looking-at "\\s-*\\_<do\\_>")
		     (not (js--re-search-forward
			   "\\_<while\\_>" (point-at-eol) t))
		     (= (current-indentation) saved-indent)))))))))


(defun js--ctrl-statement-indentation ()
  "Helper function for `js--proper-indentation'.
Return the proper indentation of the current line if it starts
the body of a control statement without braces; otherwise, return
nil."
  (save-excursion
    (back-to-indentation)
    (when (save-excursion
            (and (not (eq (point-at-bol) (point-min)))
                 (not (looking-at "[{]"))
                 (js--re-search-backward "[[:graph:]]" nil t)
                 (progn
                   (or (eobp) (forward-char))
                   (when (= (char-before) ?\)) (backward-list))
                   (skip-syntax-backward " ")
                   (skip-syntax-backward "w_")
                   (looking-at js--possibly-braceless-keyword-re))
                 (memq (char-before) '(?\s ?\t ?\n ?\}))
                 (not (js--end-of-do-while-loop-p))))
      (save-excursion
        (goto-char (match-beginning 0))
        (+ (current-indentation) js-indent-level)))))

(defun js--get-c-offset (symbol anchor)
  (let ((c-offsets-alist
         (list (cons 'c js-comment-lineup-func))))
    (c-get-syntactic-indentation (list (cons symbol anchor)))))

(defun js--same-line (pos)
  (and (>= pos (point-at-bol))
       (<= pos (point-at-eol))))

(defun js--multi-line-declaration-indentation ()
  "Helper function for `js--proper-indentation'.
Return the proper indentation of the current line if it belongs to a declaration
statement spanning multiple lines; otherwise, return nil."
  (let (forward-sexp-function ; Use Lisp version.
        at-opening-bracket)
    (save-excursion
      (back-to-indentation)
      (when (not (looking-at js--declaration-keyword-re))
        (when (looking-at js--indent-operator-re)
          (goto-char (match-end 0)))
        (while (and (not at-opening-bracket)
                    (not (bobp))
                    (let ((pos (point)))
                      (save-excursion
                        (js--backward-syntactic-ws)
                        (or (eq (char-before) ?,)
                            (and (not (eq (char-before) ?\;))
                                 (prog2
                                     (skip-syntax-backward ".")
                                     (looking-at js--indent-operator-re)
                                   (js--backward-syntactic-ws))
                                 (not (eq (char-before) ?\;)))
                            (js--same-line pos)))))
          (condition-case nil
              (backward-sexp)
            (scan-error (setq at-opening-bracket t))))
        (when (looking-at js--declaration-keyword-re)
          (goto-char (match-end 0))
          (1+ (current-column)))))))

(defun js--indent-in-array-comp (bracket)
  "Return non-nil if we think we're in an array comprehension.
In particular, return the buffer position of the first `for' kwd."
  (let ((end (point)))
    (save-excursion
      (goto-char bracket)
      (when (looking-at "\\[")
        (forward-char 1)
        (js--forward-syntactic-ws)
        (if (looking-at "[[{]")
            (let (forward-sexp-function) ; Use Lisp version.
              (forward-sexp)             ; Skip destructuring form.
              (js--forward-syntactic-ws)
              (if (and (/= (char-after) ?,) ; Regular array.
                       (looking-at "for"))
                  (match-beginning 0)))
          ;; To skip arbitrary expressions we need the parser,
          ;; so we'll just guess at it.
          (if (and (> end (point)) ; Not empty literal.
                   (re-search-forward "[^,]]* \\(for\\_>\\)" end t)
                   ;; Not inside comment or string literal.
                   (let ((status (parse-partial-sexp bracket (point))))
                     (and (= 1 (car status))
                          (not (nth 8 status)))))
              (match-beginning 1)))))))

(defun js--array-comp-indentation (bracket for-kwd)
  (if (js--same-line for-kwd)
      ;; First continuation line.
      (save-excursion
        (goto-char bracket)
        (forward-char 1)
        (skip-chars-forward " \t")
        (current-column))
    (save-excursion
      (goto-char for-kwd)
      (current-column))))

(defun js--maybe-goto-declaration-keyword-end (parse-status)
  "Helper function for `js--proper-indentation'.
Depending on the value of `js-indent-first-init', move
point to the end of a variable declaration keyword so that
indentation is aligned to that column."
  (cond
   ((eq js-indent-first-init t)
    (when (looking-at js--declaration-keyword-re)
      (goto-char (1+ (match-end 0)))))
   ((eq js-indent-first-init 'dynamic)
    (let ((bracket (nth 1 parse-status))
          declaration-keyword-end
          at-closing-bracket-p
          forward-sexp-function ; Use Lisp version.
          comma-p)
      (when (looking-at js--declaration-keyword-re)
        (setq declaration-keyword-end (match-end 0))
        (save-excursion
          (goto-char bracket)
          (setq at-closing-bracket-p
                (condition-case nil
                    (progn
                      (forward-sexp)
                      t)
                  (error nil)))
          (when at-closing-bracket-p
            (while (forward-comment 1))
            (setq comma-p (looking-at-p ","))))
        (when comma-p
          (goto-char (1+ declaration-keyword-end))))))))

(defun js--proper-indentation (parse-status)
  "Return the proper indentation for the current line."
  (save-excursion
    (back-to-indentation)
    (cond ((nth 4 parse-status)    ; inside comment
           (js--get-c-offset 'c (nth 8 parse-status)))
          ((nth 3 parse-status) 0) ; inside string
          ((eq (char-after) ?#) 0)
          ((save-excursion (js--beginning-of-macro)) 4)
          ;; Indent array comprehension continuation lines specially.
          ((let ((bracket (nth 1 parse-status))
                 beg)
             (and bracket
                  (not (js--same-line bracket))
                  (setq beg (js--indent-in-array-comp bracket))
                  ;; At or after the first loop?
                  (>= (point) beg)
                  (js--array-comp-indentation bracket beg))))
          ((js--chained-expression-p))
          ((js--ctrl-statement-indentation))
          ((js--multi-line-declaration-indentation))
          ((nth 1 parse-status)
	   ;; A single closing paren/bracket should be indented at the
	   ;; same level as the opening statement. Same goes for
	   ;; "case" and "default".
           (let ((same-indent-p (looking-at "[]})]"))
                 (switch-keyword-p (looking-at "default\\_>\\|case\\_>[^:]"))
                 (continued-expr-p (js--continued-expression-p)))
             (goto-char (nth 1 parse-status)) ; go to the opening char
             (if (looking-at "[({[]\\s-*\\(/[/*]\\|$\\)")
                 (progn ; nothing following the opening paren/bracket
                   (skip-syntax-backward " ")
                   (when (eq (char-before) ?\)) (backward-list))
                   (back-to-indentation)
                   (js--maybe-goto-declaration-keyword-end parse-status)
                   (let* ((in-switch-p (unless same-indent-p
                                         (looking-at "\\_<switch\\_>")))
                          (same-indent-p (or same-indent-p
                                             (and switch-keyword-p
                                                  in-switch-p)))
                          (indent
                           (cond (same-indent-p
                                  (current-column))
                                 (continued-expr-p
                                  (+ (current-column) (* 2 js-indent-level)
                                     js-expr-indent-offset))
                                 (t
                                  (+ (current-column) js-indent-level
                                     (pcase (char-after (nth 1 parse-status))
                                       (?\( js-paren-indent-offset)
                                       (?\[ js-square-indent-offset)
                                       (?\{ js-curly-indent-offset)))))))
                     (if in-switch-p
                         (+ indent js-switch-indent-offset)
                       indent)))
               ;; If there is something following the opening
               ;; paren/bracket, everything else should be indented at
               ;; the same level.
               (unless same-indent-p
                 (forward-char)
                 (skip-chars-forward " \t"))
               (current-column))))

          ((js--continued-expression-p)
           (+ js-indent-level js-expr-indent-offset))
          (t (prog-first-column)))))

;;; JSX Indentation

(defsubst js--jsx-find-before-tag ()
  "Find where JSX starts.

Assume JSX appears in the following instances:
- Inside parentheses, when returned or as the first argument
  to a function, and after a newline
- When assigned to variables or object properties, but only
  on a single line
- As the N+1th argument to a function

This is an optimized version of (re-search-backward \"[(,]\n\"
nil t), except set point to the end of the match.  This logic
executes up to the number of lines in the file, so it should be
really fast to reduce that impact."
  (let (pos)
    (while (and (> (point) (point-min))
                (not (progn
                       (end-of-line 0)
                       (when (or (eq (char-before) 40)   ; (
                                 (eq (char-before) 44))  ; ,
                         (setq pos (1- (point))))))))
    pos))

(defconst js--jsx-end-tag-re
  (concat "</" sgml-name-re ">\\|/>")
  "Find the end of a JSX element.")

(defconst js--jsx-after-tag-re "[),]"
  "Find where JSX ends.
This complements the assumption of where JSX appears from
`js--jsx-before-tag-re', which see.")

(defun js--jsx-indented-element-p ()
  "Determine if/how the current line should be indented as JSX.

Return `first' for the first JSXElement on its own line.
Return `nth' for subsequent lines of the first JSXElement.
Return `expression' for an embedded JS expression.
Return `after' for anything after the last JSXElement.
Return nil for non-JSX lines.

Currently, JSX indentation supports the following styles:

- Single-line elements (indented like normal JS):

  var element = <div></div>;

- Multi-line elements (enclosed in parentheses):

  function () {
    return (
      <div>
        <div></div>
      </div>
    );
 }

- Function arguments:

  React.render(
    <div></div>,
    document.querySelector('.root')
  );"
  (let ((current-pos (point))
        (current-line (line-number-at-pos))
        last-pos
        before-tag-pos before-tag-line
        tag-start-pos tag-start-line
        tag-end-pos tag-end-line
        after-tag-line
        parens paren type)
    (save-excursion
      (and
       ;; Determine if we're inside a jsx element
       (progn
         (end-of-line)
         (while (and (not tag-start-pos)
                     (setq last-pos (js--jsx-find-before-tag)))
           (while (forward-comment 1))
           (when (= (char-after) 60) ; <
             (setq before-tag-pos last-pos
                   tag-start-pos (point)))
           (goto-char last-pos))
         tag-start-pos)
       (progn
         (setq before-tag-line (line-number-at-pos before-tag-pos)
               tag-start-line (line-number-at-pos tag-start-pos))
         (and
          ;; A "before" line which also starts an element begins with js, so
          ;; indent it like js
          (> current-line before-tag-line)
          ;; Only indent the jsx lines like jsx
          (>= current-line tag-start-line)))
       (cond
        ;; Analyze bounds if there are any
        ((progn
           (while (and (not tag-end-pos)
                       (setq last-pos (re-search-forward js--jsx-end-tag-re nil t)))
             (while (forward-comment 1))
             (when (looking-at js--jsx-after-tag-re)
               (setq tag-end-pos last-pos)))
           tag-end-pos)
         (setq tag-end-line (line-number-at-pos tag-end-pos)
               after-tag-line (line-number-at-pos after-tag-line))
         (or (and
              ;; Ensure we're actually within the bounds of the jsx
              (<= current-line tag-end-line)
              ;; An "after" line which does not end an element begins with
              ;; js, so indent it like js
              (<= current-line after-tag-line))
             (and
              ;; Handle another case where there could be e.g. comments after
              ;; the element
              (> current-line tag-end-line)
              (< current-line after-tag-line)
              (setq type 'after))))
        ;; They may not be any bounds (yet)
        (t))
       ;; Check if we're inside an embedded multi-line js expression
       (cond
        ((not type)
         (goto-char current-pos)
         (end-of-line)
         (setq parens (nth 9 (syntax-ppss)))
         (while (and parens (not type))
           (setq paren (car parens))
           (cond
            ((and (>= paren tag-start-pos)
                  ;; Curly bracket indicates the start of an embedded expression
                  (= (char-after paren) 123) ; {
                  ;; The first line of the expression is indented like sgml
                  (> current-line (line-number-at-pos paren))
                  ;; Check if within a closing curly bracket (if any)
                  ;; (exclusive, as the closing bracket is indented like sgml)
                  (cond
                   ((progn
                      (goto-char paren)
                      (ignore-errors (let (forward-sexp-function)
                                       (forward-sexp))))
                    (< current-line (line-number-at-pos)))
                   (t)))
             ;; Indicate this guy will be indented specially
             (setq type 'expression))
            (t (setq parens (cdr parens)))))
         t)
        (t))
       (cond
        (type)
        ;; Indent the first jsx thing like js so we can indent future jsx things
        ;; like sgml relative to the first thing
        ((= current-line tag-start-line) 'first)
        ('nth))))))

(defmacro js--as-sgml (&rest body)
  "Execute BODY as if in sgml-mode."
  `(with-syntax-table sgml-mode-syntax-table
     (let (forward-sexp-function
           parse-sexp-lookup-properties)
       ,@body)))

(defun js--expression-in-sgml-indent-line ()
  "Indent the current line as JavaScript or SGML (whichever is farther)."
  (let* (indent-col
         (savep (point))
         ;; Don't whine about errors/warnings when we're indenting.
         ;; This has to be set before calling parse-partial-sexp below.
         (inhibit-point-motion-hooks t)
         (parse-status (save-excursion
                         (syntax-ppss (point-at-bol)))))
    ;; Don't touch multiline strings.
    (unless (nth 3 parse-status)
      (setq indent-col (save-excursion
                         (back-to-indentation)
                         (if (>= (point) savep) (setq savep nil))
                         (js--as-sgml (sgml-calculate-indent))))
      (if (null indent-col)
          'noindent
        ;; Use whichever indentation column is greater, such that the sgml
        ;; column is effectively a minimum
        (setq indent-col (max (js--proper-indentation parse-status)
                              (+ indent-col js-indent-level)))
        (if savep
            (save-excursion (indent-line-to indent-col))
          (indent-line-to indent-col))))))

(defun js-indent-line ()
  "Indent the current line as JavaScript."
  (interactive)
  (let* ((parse-status
          (save-excursion (syntax-ppss (point-at-bol))))
         (offset (- (point) (save-excursion (back-to-indentation) (point)))))
    (unless (nth 3 parse-status)
      (indent-line-to (js--proper-indentation parse-status))
      (when (> offset 0) (forward-char offset)))))

(defun js-jsx-indent-line ()
  "Indent the current line as JSX (with SGML offsets).
i.e., customize JSX element indentation with `sgml-basic-offset',
`sgml-attribute-offset' et al."
  (interactive)
  (let ((indentation-type (js--jsx-indented-element-p)))
    (cond
     ((eq indentation-type 'expression)
      (js--expression-in-sgml-indent-line))
     ((or (eq indentation-type 'first)
          (eq indentation-type 'after))
      ;; Don't treat this first thing as a continued expression (often a "<" or
      ;; ">" causes this misinterpretation)
      (cl-letf (((symbol-function #'js--continued-expression-p) 'ignore))
        (js-indent-line)))
     ((eq indentation-type 'nth)
      (js--as-sgml (sgml-indent-line)))
     (t (js-indent-line)))))

;;; Filling

(defvar js--filling-paragraph nil)

;; FIXME: Such redefinitions are bad style.  We should try and use some other
;; way to get the same result.
(defadvice c-forward-sws (around js-fill-paragraph activate)
  (if js--filling-paragraph
      (setq ad-return-value (js--forward-syntactic-ws (ad-get-arg 0)))
    ad-do-it))

(defadvice c-backward-sws (around js-fill-paragraph activate)
  (if js--filling-paragraph
      (setq ad-return-value (js--backward-syntactic-ws (ad-get-arg 0)))
    ad-do-it))

(defadvice c-beginning-of-macro (around js-fill-paragraph activate)
  (if js--filling-paragraph
      (setq ad-return-value (js--beginning-of-macro (ad-get-arg 0)))
    ad-do-it))

(defun js-c-fill-paragraph (&optional justify)
  "Fill the paragraph with `c-fill-paragraph'."
  (interactive "*P")
  (let ((js--filling-paragraph t)
        (fill-paragraph-function #'c-fill-paragraph))
    (c-fill-paragraph justify)))

;;; Type database and Imenu

;; We maintain a cache of semantic information, i.e., the classes and
;; functions we've encountered so far. In order to avoid having to
;; re-parse the buffer on every change, we cache the parse state at
;; each interesting point in the buffer. Each parse state is a
;; modified copy of the previous one, or in the case of the first
;; parse state, the empty state.
;;
;; The parse state itself is just a stack of js--pitem
;; instances. It starts off containing one element that is never
;; closed, that is initially js--initial-pitem.
;;


(defun js--pitem-format (pitem)
  (let ((name (js--pitem-name pitem))
        (type (js--pitem-type pitem)))

    (format "name:%S type:%S"
            name
            (if (atom type)
                type
              (plist-get type :name)))))

(defun js--make-merged-item (item child name-parts)
  "Helper function for `js--splice-into-items'.
Return a new item that is the result of merging CHILD into
ITEM.  NAME-PARTS is a list of parts of the name of CHILD
that we haven't consumed yet."
  (js--debug "js--make-merged-item: {%s} into {%s}"
                   (js--pitem-format child)
                   (js--pitem-format item))

  ;; If the item we're merging into isn't a class, make it into one
  (unless (consp (js--pitem-type item))
    (js--debug "js--make-merged-item: changing dest into class")
    (setq item (make-js--pitem
                :children (list item)

                ;; Use the child's class-style if it's available
                :type (if (atom (js--pitem-type child))
                          js--dummy-class-style
                  (js--pitem-type child))

                :name (js--pitem-strname item))))

  ;; Now we can merge either a function or a class into a class
  (cons (cond
         ((cdr name-parts)
          (js--debug "js--make-merged-item: recursing")
          ;; if we have more name-parts to go before we get to the
          ;; bottom of the class hierarchy, call the merger
          ;; recursively
          (js--splice-into-items (car item) child
                                       (cdr name-parts)))

         ((atom (js--pitem-type child))
          (js--debug "js--make-merged-item: straight merge")
          ;; Not merging a class, but something else, so just prepend
          ;; it
          (cons child (car item)))

         (t
          ;; Otherwise, merge the new child's items into those
          ;; of the new class
          (js--debug "js--make-merged-item: merging class contents")
          (append (car child) (car item))))
        (cdr item)))

(defun js--pitem-strname (pitem)
  "Last part of the name of PITEM, as a string or symbol."
  (let ((name (js--pitem-name pitem)))
    (if (consp name)
        (car (last name))
      name)))

(defun js--splice-into-items (items child name-parts)
  "Splice CHILD into the `js--pitem' ITEMS at NAME-PARTS.
If a class doesn't exist in the tree, create it.  Return
the new items list.  NAME-PARTS is a list of strings given
the broken-down class name of the item to insert."

  (let ((top-name (car name-parts))
        (item-ptr items)
        new-items last-new-item new-cons)

    (js--debug "js--splice-into-items: name-parts: %S items:%S"
             name-parts
             (mapcar #'js--pitem-name items))

    (cl-assert (stringp top-name))
    (cl-assert (> (length top-name) 0))

    ;; If top-name isn't found in items, then we build a copy of items
    ;; and throw it away. But that's okay, since most of the time, we
    ;; *will* find an instance.

    (while (and item-ptr
                (cond ((equal (js--pitem-strname (car item-ptr)) top-name)
                       ;; Okay, we found an entry with the right name. Splice
                       ;; the merged item into the list...
                       (setq new-cons (cons (js--make-merged-item
                                             (car item-ptr) child
                                             name-parts)
                                            (cdr item-ptr)))

                       (if last-new-item
                           (setcdr last-new-item new-cons)
                         (setq new-items new-cons))

                       ;; ...and terminate the loop
                       nil)

                      (t
                       ;; Otherwise, copy the current cons and move onto the
                       ;; text. This is tricky; we keep track of the tail of
                       ;; the list that begins with new-items in
                       ;; last-new-item.
                       (setq new-cons (cons (car item-ptr) nil))
                       (if last-new-item
                           (setcdr last-new-item new-cons)
                         (setq new-items new-cons))
                       (setq last-new-item new-cons)

                       ;; Go to the next cell in items
                       (setq item-ptr (cdr item-ptr))))))

    (if item-ptr
        ;; Yay! We stopped because we found something, not because
        ;; we ran out of items to search. Just return the new
        ;; list.
        (progn
          (js--debug "search succeeded: %S" name-parts)
          new-items)

      ;; We didn't find anything. If the child is a class and we don't
      ;; have any classes to drill down into, just push that class;
      ;; otherwise, make a fake class and carry on.
      (js--debug "search failed: %S" name-parts)
      (cons (if (cdr name-parts)
                ;; We have name-parts left to process. Make a fake
                ;; class for this particular part...
                (make-js--pitem
                 ;; ...and recursively digest the rest of the name
                 :children (js--splice-into-items
                            nil child (cdr name-parts))
                 :type js--dummy-class-style
                 :name top-name)

              ;; Otherwise, this is the only name we have, so stick
              ;; the item on the front of the list
              child)
            items))))

(defun js--pitem-add-child (pitem child)
  "Copy `js--pitem' PITEM, and push CHILD onto its list of children."
  (cl-assert (integerp (js--pitem-h-begin child)))
  (cl-assert (if (consp (js--pitem-name child))
              (cl-loop for part in (js--pitem-name child)
                       always (stringp part))
            t))

  ;; This trick works because we know (based on our defstructs) that
  ;; the child list is always the first element, and so the second
  ;; element and beyond can be shared when we make our "copy".
  (cons

   (let ((name (js--pitem-name child))
         (type (js--pitem-type child)))

     (cond ((cdr-safe name) ; true if a list of at least two elements
            ;; Use slow path because we need class lookup
            (js--splice-into-items (car pitem) child name))

           ((and (consp type)
                 (plist-get type :prototype))

            ;; Use slow path because we need class merging. We know
            ;; name is a list here because down in
            ;; `js--ensure-cache', we made sure to only add
            ;; class entries with lists for :name
            (cl-assert (consp name))
            (js--splice-into-items (car pitem) child name))

           (t
            ;; Fast path
            (cons child (car pitem)))))

   (cdr pitem)))

(defun js--maybe-make-marker (location)
  "Return a marker for LOCATION if `imenu-use-markers' is non-nil."
  (if imenu-use-markers
      (set-marker (make-marker) location)
    location))

(defun js--pitems-to-imenu (pitems unknown-ctr)
  "Convert PITEMS, a list of `js--pitem' structures, to imenu format."

  (let (imenu-items pitem pitem-type pitem-name subitems)

    (while (setq pitem (pop pitems))
      (setq pitem-type (js--pitem-type pitem))
      (setq pitem-name (js--pitem-strname pitem))
      (when (eq pitem-name t)
        (setq pitem-name (format "[unknown %s]"
                                 (cl-incf (car unknown-ctr)))))

      (cond
       ((memq pitem-type '(function macro))
        (cl-assert (integerp (js--pitem-h-begin pitem)))
        (push (cons pitem-name
                    (js--maybe-make-marker
                     (js--pitem-h-begin pitem)))
              imenu-items))

       ((consp pitem-type) ; class definition
        (setq subitems (js--pitems-to-imenu
                        (js--pitem-children pitem)
                        unknown-ctr))
        (cond (subitems
               (push (cons pitem-name subitems)
                     imenu-items))

              ((js--pitem-h-begin pitem)
               (cl-assert (integerp (js--pitem-h-begin pitem)))
               (setq subitems (list
                               (cons "[empty]"
                                     (js--maybe-make-marker
                                      (js--pitem-h-begin pitem)))))
               (push (cons pitem-name subitems)
                     imenu-items))))

       (t (error "Unknown item type: %S" pitem-type))))

    imenu-items))

(defun js--imenu-create-index ()
  "Return an imenu index for the current buffer."
  (save-excursion
    (save-restriction
      (widen)
      (goto-char (point-max))
      (js--ensure-cache)
      (cl-assert (or (= (point-min) (point-max))
                  (eq js--last-parse-pos (point))))
      (when js--last-parse-pos
        (let ((state js--state-at-last-parse-pos)
              (unknown-ctr (cons -1 nil)))

          ;; Make sure everything is closed
          (while (cdr state)
            (setq state
                  (cons (js--pitem-add-child (cl-second state) (car state))
                        (cddr state))))

          (cl-assert (= (length state) 1))

          ;; Convert the new-finalized state into what imenu expects
          (js--pitems-to-imenu
           (car (js--pitem-children state))
           unknown-ctr))))))

;; Silence the compiler.
(defvar which-func-imenu-joiner-function)

(defun js--which-func-joiner (parts)
  (mapconcat #'identity parts "."))

(defun js--imenu-to-flat (items prefix symbols)
  (cl-loop for item in items
           if (imenu--subalist-p item)
           do (js--imenu-to-flat
               (cdr item) (concat prefix (car item) ".")
               symbols)
           else
           do (let* ((name (concat prefix (car item)))
                     (name2 name)
                     (ctr 0))

                (while (gethash name2 symbols)
                  (setq name2 (format "%s<%d>" name (cl-incf ctr))))

                (puthash name2 (cdr item) symbols))))

(defun js--get-all-known-symbols ()
  "Return a hash table of all JavaScript symbols.
This searches all existing `js-mode' buffers. Each key is the
name of a symbol (possibly disambiguated with <N>, where N > 1),
and each value is a marker giving the location of that symbol."
  (cl-loop with symbols = (make-hash-table :test 'equal)
           with imenu-use-markers = t
           for buffer being the buffers
           for imenu-index = (with-current-buffer buffer
                               (when (derived-mode-p 'js-mode)
                                 (js--imenu-create-index)))
           do (js--imenu-to-flat imenu-index "" symbols)
           finally return symbols))

(defvar js--symbol-history nil
  "History of entered JavaScript symbols.")

(defun js--read-symbol (symbols-table prompt &optional initial-input)
  "Helper function for `js-find-symbol'.
Read a symbol from SYMBOLS-TABLE, which is a hash table like the
one from `js--get-all-known-symbols', using prompt PROMPT and
initial input INITIAL-INPUT.  Return a cons of (SYMBOL-NAME
. LOCATION), where SYMBOL-NAME is a string and LOCATION is a
marker."
  (unless ido-mode
    (ido-mode 1)
    (ido-mode -1))

  (let ((choice (ido-completing-read
                 prompt
                 (cl-loop for key being the hash-keys of symbols-table
                          collect key)
                 nil t initial-input 'js--symbol-history)))
    (cons choice (gethash choice symbols-table))))

(defun js--guess-symbol-at-point ()
  (let ((bounds (bounds-of-thing-at-point 'symbol)))
    (when bounds
      (save-excursion
        (goto-char (car bounds))
        (when (eq (char-before) ?.)
          (backward-char)
          (setf (car bounds) (point))))
      (buffer-substring (car bounds) (cdr bounds)))))

(defvar find-tag-marker-ring)           ; etags

;; etags loads ring.
(declare-function ring-insert "ring" (ring item))

(defun js-find-symbol (&optional arg)
  "Read a JavaScript symbol and jump to it.
With a prefix argument, restrict symbols to those from the
current buffer.  Pushes a mark onto the tag ring just like
`find-tag'."
  (interactive "P")
  (require 'etags)
  (let (symbols marker)
    (if (not arg)
        (setq symbols (js--get-all-known-symbols))
      (setq symbols (make-hash-table :test 'equal))
      (js--imenu-to-flat (js--imenu-create-index)
                               "" symbols))

    (setq marker (cdr (js--read-symbol
                       symbols "Jump to: "
                       (js--guess-symbol-at-point))))

    (ring-insert find-tag-marker-ring (point-marker))
    (switch-to-buffer (marker-buffer marker))
    (push-mark)
    (goto-char marker)))

;;; MozRepl integration

(define-error 'js-moz-bad-rpc "Mozilla RPC Error") ;; '(timeout error))
(define-error 'js-js-error "JavaScript Error") ;; '(js-error error))

(defun js--wait-for-matching-output
  (process regexp timeout &optional start)
  "Wait TIMEOUT seconds for PROCESS to output a match for REGEXP.
On timeout, return nil.  On success, return t with match data
set.  If START is non-nil, look for output starting from START.
Otherwise, use the current value of `process-mark'."
  (with-current-buffer (process-buffer process)
    (cl-loop with start-pos = (or start
                                  (marker-position (process-mark process)))
             with end-time = (+ (float-time) timeout)
             for time-left = (- end-time (float-time))
             do (goto-char (point-max))
             if (looking-back regexp start-pos) return t
             while (> time-left 0)
             do (accept-process-output process time-left nil t)
             do (goto-char (process-mark process))
             finally do (signal
                         'js-moz-bad-rpc
                         (list (format "Timed out waiting for output matching %S" regexp))))))

(cl-defstruct js--js-handle
  ;; Integer, mirrors the value we see in JS
  (id nil :read-only t)

  ;; Process to which this thing belongs
  (process nil :read-only t))

(defun js--js-handle-expired-p (x)
  (not (eq (js--js-handle-process x)
           (inferior-moz-process))))

(defvar js--js-references nil
  "Maps Elisp JavaScript proxy objects to their JavaScript IDs.")

(defvar js--js-process nil
  "The most recent MozRepl process object.")

(defvar js--js-gc-idle-timer nil
  "Idle timer for cleaning up JS object references.")

(defvar js--js-last-gcs-done nil)

(defconst js--moz-interactor
  (replace-regexp-in-string
   "[ \n]+" " "
   ; */" Make Emacs happy
"(function(repl) {
  repl.defineInteractor('js', {
    onStart: function onStart(repl) {
      if(!repl._jsObjects) {
        repl._jsObjects = {};
        repl._jsLastID = 0;
        repl._jsGC = this._jsGC;
      }
      this._input = '';
    },

    _jsGC: function _jsGC(ids_in_use) {
      var objects = this._jsObjects;
      var keys = [];
      var num_freed = 0;

      for(var pn in objects) {
        keys.push(Number(pn));
      }

      keys.sort(function(x, y) x - y);
      ids_in_use.sort(function(x, y) x - y);
      var i = 0;
      var j = 0;

      while(i < ids_in_use.length && j < keys.length) {
        var id = ids_in_use[i++];
        while(j < keys.length && keys[j] !== id) {
          var k_id = keys[j++];
          delete objects[k_id];
          ++num_freed;
        }
        ++j;
      }

      while(j < keys.length) {
        var k_id = keys[j++];
        delete objects[k_id];
        ++num_freed;
      }

      return num_freed;
    },

    _mkArray: function _mkArray() {
      var result = [];
      for(var i = 0; i < arguments.length; ++i) {
        result.push(arguments[i]);
      }
      return result;
    },

    _parsePropDescriptor: function _parsePropDescriptor(parts) {
      if(typeof parts === 'string') {
        parts = [ parts ];
      }

      var obj = parts[0];
      var start = 1;

      if(typeof obj === 'string') {
        obj = window;
        start = 0;
      } else if(parts.length < 2) {
        throw new Error('expected at least 2 arguments');
      }

      for(var i = start; i < parts.length - 1; ++i) {
        obj = obj[parts[i]];
      }

      return [obj, parts[parts.length - 1]];
    },

    _getProp: function _getProp(/*...*/) {
      if(arguments.length === 0) {
        throw new Error('no arguments supplied to getprop');
      }

      if(arguments.length === 1 &&
         (typeof arguments[0]) !== 'string')
      {
        return arguments[0];
      }

      var [obj, propname] = this._parsePropDescriptor(arguments);
      return obj[propname];
    },

    _putProp: function _putProp(properties, value) {
      var [obj, propname] = this._parsePropDescriptor(properties);
      obj[propname] = value;
    },

    _delProp: function _delProp(propname) {
      var [obj, propname] = this._parsePropDescriptor(arguments);
      delete obj[propname];
    },

    _typeOf: function _typeOf(thing) {
      return typeof thing;
    },

    _callNew: function(constructor) {
      if(typeof constructor === 'string')
      {
        constructor = window[constructor];
      } else if(constructor.length === 1 &&
                typeof constructor[0] !== 'string')
      {
        constructor = constructor[0];
      } else {
        var [obj,propname] = this._parsePropDescriptor(constructor);
        constructor = obj[propname];
      }

      /* Hacky, but should be robust */
      var s = 'new constructor(';
      for(var i = 1; i < arguments.length; ++i) {
        if(i != 1) {
          s += ',';
        }

        s += 'arguments[' + i + ']';
      }

      s += ')';
      return eval(s);
    },

    _callEval: function(thisobj, js) {
      return eval.call(thisobj, js);
    },

    getPrompt: function getPrompt(repl) {
      return 'EVAL>'
    },

    _lookupObject: function _lookupObject(repl, id) {
      if(typeof id === 'string') {
        switch(id) {
        case 'global':
          return window;
        case 'nil':
          return null;
        case 't':
          return true;
        case 'false':
          return false;
        case 'undefined':
          return undefined;
        case 'repl':
          return repl;
        case 'interactor':
          return this;
        case 'NaN':
          return NaN;
        case 'Infinity':
          return Infinity;
        case '-Infinity':
          return -Infinity;
        default:
          throw new Error('No object with special id:' + id);
        }
      }

      var ret = repl._jsObjects[id];
      if(ret === undefined) {
        throw new Error('No object with id:' + id + '(' + typeof id + ')');
      }
      return ret;
    },

    _findOrAllocateObject: function _findOrAllocateObject(repl, value) {
      if(typeof value !== 'object'  && typeof value !== 'function') {
        throw new Error('_findOrAllocateObject called on non-object('
                        + typeof(value) + '): '
                        + value)
      }

      for(var id in repl._jsObjects) {
        id = Number(id);
        var obj = repl._jsObjects[id];
        if(obj === value) {
          return id;
        }
      }

      var id = ++repl._jsLastID;
      repl._jsObjects[id] = value;
      return id;
    },

    _fixupList: function _fixupList(repl, list) {
      for(var i = 0; i < list.length; ++i) {
        if(list[i] instanceof Array) {
          this._fixupList(repl, list[i]);
        } else if(typeof list[i] === 'object') {
          var obj = list[i];
          if(obj.funcall) {
            var parts = obj.funcall;
            this._fixupList(repl, parts);
            var [thisobj, func] = this._parseFunc(parts[0]);
            list[i] = func.apply(thisobj, parts.slice(1));
          } else if(obj.objid) {
            list[i] = this._lookupObject(repl, obj.objid);
          } else {
            throw new Error('Unknown object type: ' + obj.toSource());
          }
        }
      }
    },

    _parseFunc: function(func) {
      var thisobj = null;

      if(typeof func === 'string') {
        func = window[func];
      } else if(func instanceof Array) {
        if(func.length === 1 && typeof func[0] !== 'string') {
          func = func[0];
        } else {
          [thisobj, func] = this._parsePropDescriptor(func);
          func = thisobj[func];
        }
      }

      return [thisobj,func];
    },

    _encodeReturn: function(value, array_as_mv) {
      var ret;

      if(value === null) {
        ret = ['special', 'null'];
      } else if(value === true) {
        ret = ['special', 'true'];
      } else if(value === false) {
        ret = ['special', 'false'];
      } else if(value === undefined) {
        ret = ['special', 'undefined'];
      } else if(typeof value === 'number') {
        if(isNaN(value)) {
          ret = ['special', 'NaN'];
        } else if(value === Infinity) {
          ret = ['special', 'Infinity'];
        } else if(value === -Infinity) {
          ret = ['special', '-Infinity'];
        } else {
          ret = ['atom', value];
        }
      } else if(typeof value === 'string') {
        ret = ['atom', value];
      } else if(array_as_mv && value instanceof Array) {
        ret = ['array', value.map(this._encodeReturn, this)];
      } else {
        ret = ['objid', this._findOrAllocateObject(repl, value)];
      }

      return ret;
    },

    _handleInputLine: function _handleInputLine(repl, line) {
      var ret;
      var array_as_mv = false;

      try {
        if(line[0] === '*') {
          array_as_mv = true;
          line = line.substring(1);
        }
        var parts = eval(line);
        this._fixupList(repl, parts);
        var [thisobj, func] = this._parseFunc(parts[0]);
        ret = this._encodeReturn(
          func.apply(thisobj, parts.slice(1)),
          array_as_mv);
      } catch(x) {
        ret = ['error', x.toString() ];
      }

      var JSON = Components.classes['@mozilla.org/dom/json;1'].createInstance(Components.interfaces.nsIJSON);
      repl.print(JSON.encode(ret));
      repl._prompt();
    },

    handleInput: function handleInput(repl, chunk) {
      this._input += chunk;
      var match, line;
      while(match = this._input.match(/.*\\n/)) {
        line = match[0];

        if(line === 'EXIT\\n') {
          repl.popInteractor();
          repl._prompt();
          return;
        }

        this._input = this._input.substring(line.length);
        this._handleInputLine(repl, line);
      }
    }
  });
})
")

  "String to set MozRepl up into a simple-minded evaluation mode.")

(defun js--js-encode-value (x)
  "Marshall the given value for JS.
Strings and numbers are JSON-encoded.  Lists (including nil) are
made into JavaScript array literals and their contents encoded
with `js--js-encode-value'."
  (cond ((stringp x) (json-encode-string x))
        ((numberp x) (json-encode-number x))
        ((symbolp x) (format "{objid:%S}" (symbol-name x)))
        ((js--js-handle-p x)

         (when (js--js-handle-expired-p x)
           (error "Stale JS handle"))

         (format "{objid:%s}" (js--js-handle-id x)))

        ((sequencep x)
         (if (eq (car-safe x) 'js--funcall)
             (format "{funcall:[%s]}"
                     (mapconcat #'js--js-encode-value (cdr x) ","))
           (concat
            "[" (mapconcat #'js--js-encode-value x ",") "]")))
        (t
         (error "Unrecognized item: %S" x))))

(defconst js--js-prompt-regexp "\\(repl[0-9]*\\)> $")
(defconst js--js-repl-prompt-regexp "^EVAL>$")
(defvar js--js-repl-depth 0)

(defun js--js-wait-for-eval-prompt ()
  (js--wait-for-matching-output
   (inferior-moz-process)
   js--js-repl-prompt-regexp js-js-timeout

   ;; start matching against the beginning of the line in
   ;; order to catch a prompt that's only partially arrived
   (save-excursion (forward-line 0) (point))))

;; Presumably "inferior-moz-process" loads comint.
(declare-function comint-send-string "comint" (process string))
(declare-function comint-send-input "comint"
                  (&optional no-newline artificial))

(defun js--js-enter-repl ()
  (inferior-moz-process) ; called for side-effect
  (with-current-buffer inferior-moz-buffer
    (goto-char (point-max))

    ;; Do some initialization the first time we see a process
    (unless (eq (inferior-moz-process) js--js-process)
      (setq js--js-process (inferior-moz-process))
      (setq js--js-references (make-hash-table :test 'eq :weakness t))
      (setq js--js-repl-depth 0)

      ;; Send interactor definition
      (comint-send-string js--js-process js--moz-interactor)
      (comint-send-string js--js-process
                          (concat "(" moz-repl-name ")\n"))
      (js--wait-for-matching-output
       (inferior-moz-process) js--js-prompt-regexp
       js-js-timeout))

    ;; Sanity check
    (when (looking-back js--js-prompt-regexp
                        (save-excursion (forward-line 0) (point)))
      (setq js--js-repl-depth 0))

    (if (> js--js-repl-depth 0)
        ;; If js--js-repl-depth > 0, we *should* be seeing an
        ;; EVAL> prompt. If we don't, give Mozilla a chance to catch
        ;; up with us.
        (js--js-wait-for-eval-prompt)

      ;; Otherwise, tell Mozilla to enter the interactor mode
      (insert (match-string-no-properties 1)
              ".pushInteractor('js')")
      (comint-send-input nil t)
      (js--wait-for-matching-output
       (inferior-moz-process) js--js-repl-prompt-regexp
       js-js-timeout))

    (cl-incf js--js-repl-depth)))

(defun js--js-leave-repl ()
  (cl-assert (> js--js-repl-depth 0))
  (when (= 0 (cl-decf js--js-repl-depth))
    (with-current-buffer inferior-moz-buffer
      (goto-char (point-max))
      (js--js-wait-for-eval-prompt)
      (insert "EXIT")
      (comint-send-input nil t)
      (js--wait-for-matching-output
       (inferior-moz-process) js--js-prompt-regexp
       js-js-timeout))))

(defsubst js--js-not (value)
  (memq value '(nil null false undefined)))

(defsubst js--js-true (value)
  (not (js--js-not value)))

(eval-and-compile
  (defun js--optimize-arglist (arglist)
    "Convert immediate js< and js! references to deferred ones."
    (cl-loop for item in arglist
             if (eq (car-safe item) 'js<)
             collect (append (list 'list ''js--funcall
                                   '(list 'interactor "_getProp"))
                             (js--optimize-arglist (cdr item)))
             else if (eq (car-safe item) 'js>)
             collect (append (list 'list ''js--funcall
                                   '(list 'interactor "_putProp"))

                             (if (atom (cadr item))
                                 (list (cadr item))
                               (list
                                (append
                                 (list 'list ''js--funcall
                                       '(list 'interactor "_mkArray"))
                                 (js--optimize-arglist (cadr item)))))
                             (js--optimize-arglist (cddr item)))
             else if (eq (car-safe item) 'js!)
             collect (pcase-let ((`(,_ ,function . ,body) item))
                       (append (list 'list ''js--funcall
                                     (if (consp function)
                                         (cons 'list
                                               (js--optimize-arglist function))
                                       function))
                               (js--optimize-arglist body)))
             else
             collect item)))

(defmacro js--js-get-service (class-name interface-name)
    `(js! ("Components" "classes" ,class-name "getService")
        (js< "Components" "interfaces" ,interface-name)))

(defmacro js--js-create-instance (class-name interface-name)
  `(js! ("Components" "classes" ,class-name "createInstance")
        (js< "Components" "interfaces" ,interface-name)))

(defmacro js--js-qi (object interface-name)
  `(js! (,object "QueryInterface")
        (js< "Components" "interfaces" ,interface-name)))

(defmacro with-js (&rest forms)
  "Run FORMS with the Mozilla repl set up for js commands.
Inside the lexical scope of `with-js', `js?', `js!',
`js-new', `js-eval', `js-list', `js<', `js>', `js-get-service',
`js-create-instance', and `js-qi' are defined."
  (declare (indent 0) (debug t))
  `(progn
     (js--js-enter-repl)
     (unwind-protect
         (cl-macrolet ((js? (&rest body) `(js--js-true ,@body))
                       (js! (function &rest body)
                            `(js--js-funcall
                              ,(if (consp function)
                                   (cons 'list
                                         (js--optimize-arglist function))
                                 function)
                              ,@(js--optimize-arglist body)))

                       (js-new (function &rest body)
                               `(js--js-new
                                 ,(if (consp function)
                                      (cons 'list
                                            (js--optimize-arglist function))
                                    function)
                                 ,@body))

                       (js-eval (thisobj js)
                                `(js--js-eval
                                  ,@(js--optimize-arglist
                                     (list thisobj js))))

                       (js-list (&rest args)
                                `(js--js-list
                                  ,@(js--optimize-arglist args)))

                       (js-get-service (&rest args)
                                       `(js--js-get-service
                                         ,@(js--optimize-arglist args)))

                       (js-create-instance (&rest args)
                                           `(js--js-create-instance
                                             ,@(js--optimize-arglist args)))

                       (js-qi (&rest args)
                              `(js--js-qi
                                ,@(js--optimize-arglist args)))

                       (js< (&rest body) `(js--js-get
                                           ,@(js--optimize-arglist body)))
                       (js> (props value)
                            `(js--js-funcall
                              '(interactor "_putProp")
                              ,(if (consp props)
                                   (cons 'list
                                         (js--optimize-arglist props))
                                 props)
                              ,@(js--optimize-arglist (list value))
                              ))
                       (js-handle? (arg) `(js--js-handle-p ,arg)))
           ,@forms)
       (js--js-leave-repl))))

(defvar js--js-array-as-list nil
  "Whether to listify any Array returned by a Mozilla function.
If nil, the whole Array is treated as a JS symbol.")

(defun js--js-decode-retval (result)
  (pcase (intern (cl-first result))
    (`atom (cl-second result))
    (`special (intern (cl-second result)))
    (`array
     (mapcar #'js--js-decode-retval (cl-second result)))
    (`objid
     (or (gethash (cl-second result)
                  js--js-references)
         (puthash (cl-second result)
                  (make-js--js-handle
                   :id (cl-second result)
                   :process (inferior-moz-process))
                  js--js-references)))

    (`error (signal 'js-js-error (list (cl-second result))))
    (x (error "Unmatched case in js--js-decode-retval: %S" x))))

(defvar comint-last-input-end)

(defun js--js-funcall (function &rest arguments)
  "Call the Mozilla function FUNCTION with arguments ARGUMENTS.
If function is a string, look it up as a property on the global
object and use the global object for `this'.
If FUNCTION is a list with one element, use that element as the
function with the global object for `this', except that if that
single element is a string, look it up on the global object.
If FUNCTION is a list with more than one argument, use the list
up to the last value as a property descriptor and the last
argument as a function."

  (with-js
   (let ((argstr (js--js-encode-value
                  (cons function arguments))))

     (with-current-buffer inferior-moz-buffer
       ;; Actual funcall
       (when js--js-array-as-list
         (insert "*"))
       (insert argstr)
       (comint-send-input nil t)
       (js--wait-for-matching-output
        (inferior-moz-process) "EVAL>"
        js-js-timeout)
       (goto-char comint-last-input-end)

       ;; Read the result
       (let* ((json-array-type 'list)
              (result (prog1 (json-read)
                        (goto-char (point-max)))))
         (js--js-decode-retval result))))))

(defun js--js-new (constructor &rest arguments)
  "Call CONSTRUCTOR as a constructor, with arguments ARGUMENTS.
CONSTRUCTOR is a JS handle, a string, or a list of these things."
  (apply #'js--js-funcall
         '(interactor "_callNew")
         constructor arguments))

(defun js--js-eval (thisobj js)
  (js--js-funcall '(interactor "_callEval") thisobj js))

(defun js--js-list (&rest arguments)
  "Return a Lisp array resulting from evaluating each of ARGUMENTS."
  (let ((js--js-array-as-list t))
    (apply #'js--js-funcall '(interactor "_mkArray")
           arguments)))

(defun js--js-get (&rest props)
  (apply #'js--js-funcall '(interactor "_getProp") props))

(defun js--js-put (props value)
  (js--js-funcall '(interactor "_putProp") props value))

(defun js-gc (&optional force)
  "Tell the repl about any objects we don't reference anymore.
With argument, run even if no intervening GC has happened."
  (interactive)

  (when force
    (setq js--js-last-gcs-done nil))

  (let ((this-gcs-done gcs-done) keys num)
    (when (and js--js-references
               (boundp 'inferior-moz-buffer)
               (buffer-live-p inferior-moz-buffer)

               ;; Don't bother running unless we've had an intervening
               ;; garbage collection; without a gc, nothing is deleted
               ;; from the weak hash table, so it's pointless telling
               ;; MozRepl about that references we still hold
               (not (eq js--js-last-gcs-done this-gcs-done))

               ;; Are we looking at a normal prompt? Make sure not to
               ;; interrupt the user if he's doing something
               (with-current-buffer inferior-moz-buffer
                 (save-excursion
                   (goto-char (point-max))
                   (looking-back js--js-prompt-regexp
                                 (save-excursion (forward-line 0) (point))))))

      (setq keys (cl-loop for x being the hash-keys
                          of js--js-references
                          collect x))
      (setq num (js--js-funcall '(repl "_jsGC") (or keys [])))

      (setq js--js-last-gcs-done this-gcs-done)
      (when (called-interactively-p 'interactive)
        (message "Cleaned %s entries" num))

      num)))

(run-with-idle-timer 30 t #'js-gc)

(defun js-eval (js)
  "Evaluate the JavaScript in JS and return JSON-decoded result."
  (interactive "MJavaScript to evaluate: ")
  (with-js
   (let* ((content-window (js--js-content-window
                           (js--get-js-context)))
          (result (js-eval content-window js)))
     (when (called-interactively-p 'interactive)
       (message "%s" (js! "String" result)))
     result)))

(defun js--get-tabs ()
  "Enumerate all JavaScript contexts available.
Each context is a list:
   (TITLE URL BROWSER TAB TABBROWSER) for content documents
   (TITLE URL WINDOW) for windows

All tabs of a given window are grouped together.  The most recent
window is first.  Within each window, the tabs are returned
left-to-right."
  (with-js
   (let (windows)

     (cl-loop with window-mediator = (js! ("Components" "classes"
                                           "@mozilla.org/appshell/window-mediator;1"
                                           "getService")
                                          (js< "Components" "interfaces"
                                               "nsIWindowMediator"))
              with enumerator = (js! (window-mediator "getEnumerator") nil)

              while (js? (js! (enumerator "hasMoreElements")))
              for window = (js! (enumerator "getNext"))
              for window-info = (js-list window
                                         (js< window "document" "title")
                                         (js! (window "location" "toString"))
                                         (js< window "closed")
                                         (js< window "windowState"))

              unless (or (js? (cl-fourth window-info))
                         (eq (cl-fifth window-info) 2))
              do (push window-info windows))

     (cl-loop for (window title location) in windows
              collect (list title location window)

              for gbrowser = (js< window "gBrowser")
              if (js-handle? gbrowser)
              nconc (cl-loop
                     for x below (js< gbrowser "browsers" "length")
                     collect (js-list (js< gbrowser
                                           "browsers"
                                           x
                                           "contentDocument"
                                           "title")

                                      (js! (gbrowser
                                            "browsers"
                                            x
                                            "contentWindow"
                                            "location"
                                            "toString"))
                                      (js< gbrowser
                                           "browsers"
                                           x)

                                      (js! (gbrowser
                                            "tabContainer"
                                            "childNodes"
                                            "item")
                                           x)

                                      gbrowser))))))

(defvar js-read-tab-history nil)

(declare-function ido-chop "ido" (items elem))

(defun js--read-tab (prompt)
  "Read a Mozilla tab with prompt PROMPT.
Return a cons of (TYPE . OBJECT).  TYPE is either `window' or
`tab', and OBJECT is a JavaScript handle to a ChromeWindow or a
browser, respectively."

  ;; Prime IDO
  (unless ido-mode
    (ido-mode 1)
    (ido-mode -1))

  (with-js
   (let ((tabs (js--get-tabs)) selected-tab-cname
         selected-tab prev-hitab)

     ;; Disambiguate names
     (setq tabs
           (cl-loop with tab-names = (make-hash-table :test 'equal)
                    for tab in tabs
                    for cname = (format "%s (%s)"
                                        (cl-second tab) (cl-first tab))
                    for num = (cl-incf (gethash cname tab-names -1))
                    if (> num 0)
                    do (setq cname (format "%s <%d>" cname num))
                    collect (cons cname tab)))

     (cl-labels
         ((find-tab-by-cname
           (cname)
           (cl-loop for tab in tabs
                    if (equal (car tab) cname)
                    return (cdr tab)))

          (mogrify-highlighting
           (hitab unhitab)

           ;; Hack to reduce the number of
           ;; round-trips to mozilla
           (let (cmds)
             (cond
              ;; Highlighting tab
              ((cl-fourth hitab)
               (push '(js! ((cl-fourth hitab) "setAttribute")
                       "style"
                       "color: red; font-weight: bold")
                     cmds)

               ;; Highlight window proper
               (push '(js! ((cl-third hitab)
                            "setAttribute")
                       "style"
                       "border: 8px solid red")
                     cmds)

               ;; Select tab, when appropriate
               (when js-js-switch-tabs
                 (push
                  '(js> ((cl-fifth hitab) "selectedTab") (cl-fourth hitab))
                  cmds)))

              ;; Highlighting whole window
              ((cl-third hitab)
               (push '(js! ((cl-third hitab) "document"
                            "documentElement" "setAttribute")
                       "style"
                       (concat "-moz-appearance: none;"
                               "border: 8px solid red;"))
                     cmds)))

             (cond
              ;; Unhighlighting tab
              ((cl-fourth unhitab)
               (push '(js! ((cl-fourth unhitab) "setAttribute") "style" "")
                     cmds)
               (push '(js! ((cl-third unhitab) "setAttribute") "style" "")
                     cmds))

              ;; Unhighlighting window
              ((cl-third unhitab)
               (push '(js! ((cl-third unhitab) "document"
                            "documentElement" "setAttribute")
                       "style" "")
                     cmds)))

             (eval (list 'with-js
                         (cons 'js-list (nreverse cmds))))))

          (command-hook
           ()
           (let* ((tab (find-tab-by-cname (car ido-matches))))
             (mogrify-highlighting tab prev-hitab)
             (setq prev-hitab tab)))

          (setup-hook
           ()
           ;; Fiddle with the match list a bit: if our first match
           ;; is a tabbrowser window, rotate the match list until
           ;; the active tab comes up
           (let ((matched-tab (find-tab-by-cname (car ido-matches))))
             (when (and matched-tab
                        (null (cl-fourth matched-tab))
                        (equal "navigator:browser"
                               (js! ((cl-third matched-tab)
                                     "document"
                                     "documentElement"
                                     "getAttribute")
                                    "windowtype")))

               (cl-loop with tab-to-match = (js< (cl-third matched-tab)
                                                 "gBrowser"
                                                 "selectedTab")

                        for match in ido-matches
                        for candidate-tab = (find-tab-by-cname match)
                        if (eq (cl-fourth candidate-tab) tab-to-match)
                        do (setq ido-cur-list
                                 (ido-chop ido-cur-list match))
                        and return t)))

           (add-hook 'post-command-hook #'command-hook t t)))


       (unwind-protect
           ;; FIXME: Don't impose IDO on the user.
           (setq selected-tab-cname
                 (let ((ido-minibuffer-setup-hook
                        (cons #'setup-hook ido-minibuffer-setup-hook)))
                   (ido-completing-read
                    prompt
                    (mapcar #'car tabs)
                    nil t nil
                    'js-read-tab-history)))

         (when prev-hitab
           (mogrify-highlighting nil prev-hitab)
           (setq prev-hitab nil)))

       (add-to-history 'js-read-tab-history selected-tab-cname)

       (setq selected-tab (cl-loop for tab in tabs
                                   if (equal (car tab) selected-tab-cname)
                                   return (cdr tab)))

       (cons (if (cl-fourth selected-tab) 'browser 'window)
             (cl-third selected-tab))))))

(defun js--guess-eval-defun-info (pstate)
  "Helper function for `js-eval-defun'.
Return a list (NAME . CLASSPARTS), where CLASSPARTS is a list of
strings making up the class name and NAME is the name of the
function part."
  (cond ((and (= (length pstate) 3)
              (eq (js--pitem-type (cl-first pstate)) 'function)
              (= (length (js--pitem-name (cl-first pstate))) 1)
              (consp (js--pitem-type (cl-second pstate))))

         (append (js--pitem-name (cl-second pstate))
                 (list (cl-first (js--pitem-name (cl-first pstate))))))

        ((and (= (length pstate) 2)
              (eq (js--pitem-type (cl-first pstate)) 'function))

         (append
          (butlast (js--pitem-name (cl-first pstate)))
          (list (car (last (js--pitem-name (cl-first pstate)))))))

        (t (error "Function not a toplevel defun or class member"))))

(defvar js--js-context nil
  "The current JavaScript context.
This is a cons like the one returned from `js--read-tab'.
Change with `js-set-js-context'.")

(defconst js--js-inserter
  "(function(func_info,func) {
    func_info.unshift('window');
    var obj = window;
    for(var i = 1; i < func_info.length - 1; ++i) {
      var next = obj[func_info[i]];
      if(typeof next !== 'object' && typeof next !== 'function') {
        next = obj.prototype && obj.prototype[func_info[i]];
        if(typeof next !== 'object' && typeof next !== 'function') {
          alert('Could not find ' + func_info.slice(0, i+1).join('.') +
                ' or ' + func_info.slice(0, i+1).join('.') + '.prototype');
          return;
        }

        func_info.splice(i+1, 0, 'prototype');
        ++i;
      }
    }

    obj[func_info[i]] = func;
    alert('Successfully updated '+func_info.join('.'));
  })")

(defun js-set-js-context (context)
  "Set the JavaScript context to CONTEXT.
When called interactively, prompt for CONTEXT."
  (interactive (list (js--read-tab "JavaScript Context: ")))
  (setq js--js-context context))

(defun js--get-js-context ()
  "Return a valid JavaScript context.
If one hasn't been set, or if it's stale, prompt for a new one."
  (with-js
   (when (or (null js--js-context)
             (js--js-handle-expired-p (cdr js--js-context))
             (pcase (car js--js-context)
               (`window (js? (js< (cdr js--js-context) "closed")))
               (`browser (not (js? (js< (cdr js--js-context)
                                        "contentDocument"))))
               (x (error "Unmatched case in js--get-js-context: %S" x))))
     (setq js--js-context (js--read-tab "JavaScript Context: ")))
   js--js-context))

(defun js--js-content-window (context)
  (with-js
   (pcase (car context)
     (`window (cdr context))
     (`browser (js< (cdr context)
                    "contentWindow" "wrappedJSObject"))
     (x (error "Unmatched case in js--js-content-window: %S" x)))))

(defun js--make-nsilocalfile (path)
  (with-js
   (let ((file (js-create-instance "@mozilla.org/file/local;1"
                                   "nsILocalFile")))
     (js! (file "initWithPath") path)
     file)))

(defun js--js-add-resource-alias (alias path)
  (with-js
   (let* ((io-service (js-get-service "@mozilla.org/network/io-service;1"
                                                "nsIIOService"))
          (res-prot (js! (io-service "getProtocolHandler") "resource"))
          (res-prot (js-qi res-prot "nsIResProtocolHandler"))
          (path-file (js--make-nsilocalfile path))
          (path-uri (js! (io-service "newFileURI") path-file)))
     (js! (res-prot "setSubstitution") alias path-uri))))

(cl-defun js-eval-defun ()
  "Update a Mozilla tab using the JavaScript defun at point."
  (interactive)

  ;; This function works by generating a temporary file that contains
  ;; the function we'd like to insert. We then use the elisp-js bridge
  ;; to command mozilla to load this file by inserting a script tag
  ;; into the document we set. This way, debuggers and such will have
  ;; a way to find the source of the just-inserted function.
  ;;
  ;; We delete the temporary file if there's an error, but otherwise
  ;; we add an unload event listener on the Mozilla side to delete the
  ;; file.

  (save-excursion
    (let (begin end pstate defun-info temp-name defun-body)
      (js-end-of-defun)
      (setq end (point))
      (js--ensure-cache)
      (js-beginning-of-defun)
      (re-search-forward "\\_<function\\_>")
      (setq begin (match-beginning 0))
      (setq pstate (js--forward-pstate))

      (when (or (null pstate)
                (> (point) end))
        (error "Could not locate function definition"))

      (setq defun-info (js--guess-eval-defun-info pstate))

      (let ((overlay (make-overlay begin end)))
        (overlay-put overlay 'face 'highlight)
        (unwind-protect
            (unless (y-or-n-p (format "Send %s to Mozilla? "
                                      (mapconcat #'identity defun-info ".")))
              (message "") ; question message lingers until next command
              (cl-return-from js-eval-defun))
          (delete-overlay overlay)))

      (setq defun-body (buffer-substring-no-properties begin end))

      (make-directory js-js-tmpdir t)

      ;; (Re)register a Mozilla resource URL to point to the
      ;; temporary directory
      (js--js-add-resource-alias "js" js-js-tmpdir)

      (setq temp-name (make-temp-file (concat js-js-tmpdir
                                             "/js-")
                                      nil ".js"))
      (unwind-protect
          (with-js
            (with-temp-buffer
              (insert js--js-inserter)
              (insert "(")
              (insert (json-encode-list defun-info))
              (insert ",\n")
              (insert defun-body)
              (insert "\n)")
              (write-region (point-min) (point-max) temp-name
                            nil 1))

            ;; Give Mozilla responsibility for deleting this file
            (let* ((content-window (js--js-content-window
                                    (js--get-js-context)))
                   (content-document (js< content-window "document"))
                   (head (if (js? (js< content-document "body"))
                             ;; Regular content
                             (js< (js! (content-document "getElementsByTagName")
                                       "head")
                                  0)
                           ;; Chrome
                           (js< content-document "documentElement")))
                   (elem (js! (content-document "createElementNS")
                              "http://www.w3.org/1999/xhtml" "script")))

              (js! (elem "setAttribute") "type" "text/javascript")
              (js! (elem "setAttribute") "src"
                   (format "resource://js/%s"
                           (file-name-nondirectory temp-name)))

              (js! (head "appendChild") elem)

              (js! (content-window "addEventListener") "unload"
                   (js! ((js-new
                          "Function" "file"
                          "return function() { file.remove(false) }"))
                        (js--make-nsilocalfile temp-name))
                   'false)
              (setq temp-name nil)



              ))

        ;; temp-name is set to nil on success
        (when temp-name
          (delete-file temp-name))))))

;;; Main Function

;;;###autoload
(define-derived-mode js-mode prog-mode "JavaScript"
  "Major mode for editing JavaScript."
  :group 'js
  (setq-local indent-line-function #'js-indent-line)
  (setq-local beginning-of-defun-function #'js-beginning-of-defun)
  (setq-local end-of-defun-function #'js-end-of-defun)
  (setq-local open-paren-in-column-0-is-defun-start nil)
  (setq-local font-lock-defaults (list js--font-lock-keywords))
  (setq-local syntax-propertize-function #'js-syntax-propertize)
  (setq-local prettify-symbols-alist js--prettify-symbols-alist)

  (setq-local parse-sexp-ignore-comments t)
  (setq-local parse-sexp-lookup-properties t)
  (setq-local which-func-imenu-joiner-function #'js--which-func-joiner)

  ;; Comments
  (setq-local comment-start "// ")
  (setq-local comment-end "")
  (setq-local fill-paragraph-function #'js-c-fill-paragraph)

  ;; Parse cache
  (add-hook 'before-change-functions #'js--flush-caches t t)

  ;; Frameworks
  (js--update-quick-match-re)

  ;; Imenu
  (setq imenu-case-fold-search nil)
  (setq imenu-create-index-function #'js--imenu-create-index)

  ;; for filling, pretend we're cc-mode
  (setq c-comment-prefix-regexp "//+\\|\\**"
        c-paragraph-start "\\(@[[:alpha:]]+\\>\\|$\\)"
        c-paragraph-separate "$"
        c-block-comment-prefix "* "
        c-line-comment-starter "//"
        c-comment-start-regexp "/[*/]\\|\\s!"
        comment-start-skip "\\(//+\\|/\\*+\\)\\s *")
  (setq-local comment-line-break-function #'c-indent-new-comment-line)
  (setq-local c-block-comment-start-regexp "/\\*")
  (setq-local comment-multi-line t)

  (setq-local electric-indent-chars
	      (append "{}():;," electric-indent-chars)) ;FIXME: js2-mode adds "[]*".
  (setq-local electric-layout-rules
	      '((?\; . after) (?\{ . after) (?\} . before)))

  (let ((c-buffer-is-cc-mode t))
    ;; FIXME: These are normally set by `c-basic-common-init'.  Should
    ;; we call it instead?  (Bug#6071)
    (make-local-variable 'paragraph-start)
    (make-local-variable 'paragraph-separate)
    (make-local-variable 'paragraph-ignore-fill-prefix)
    (make-local-variable 'adaptive-fill-mode)
    (make-local-variable 'adaptive-fill-regexp)
    (c-setup-paragraph-variables))

  ;; Important to fontify the whole buffer syntactically! If we don't,
  ;; then we might have regular expression literals that aren't marked
  ;; as strings, which will screw up parse-partial-sexp, scan-lists,
  ;; etc. and produce maddening "unbalanced parenthesis" errors.
  ;; When we attempt to find the error and scroll to the portion of
  ;; the buffer containing the problem, JIT-lock will apply the
  ;; correct syntax to the regular expression literal and the problem
  ;; will mysteriously disappear.
  ;; FIXME: We should instead do this fontification lazily by adding
  ;; calls to syntax-propertize wherever it's really needed.
  ;;(syntax-propertize (point-max))
  )

;;;###autoload
(define-derived-mode js-jsx-mode js-mode "JSX"
  "Major mode for editing JSX.

To customize the indentation for this mode, set the SGML offset
variables (`sgml-basic-offset', `sgml-attribute-offset' et al.)
locally, like so:

  (defun set-jsx-indentation ()
    (setq-local sgml-basic-offset js-indent-level))
  (add-hook \\='js-jsx-mode-hook #\\='set-jsx-indentation)"
  :group 'js
  (setq-local indent-line-function #'js-jsx-indent-line))

;;;###autoload (defalias 'javascript-mode 'js-mode)

(eval-after-load 'folding
  '(when (fboundp 'folding-add-to-marks-list)
     (folding-add-to-marks-list 'js-mode "// {{{" "// }}}" )))

;;;###autoload
(dolist (name (list "node" "nodejs" "gjs" "rhino"))
  (add-to-list 'interpreter-mode-alist (cons (purecopy name) 'js-mode)))

(provide 'js)

;; js.el ends here