I got a bug report through Emacs Wiki (see 
http://www.emacswiki.org/cgi-bin/wiki/NxhtmlMode) saying that Emacs 
hangs when a large javascript file is opened. I tested and, yes, it 
hangs when I try to scroll down a number of times.

I have attached the javascript.el that I have used. (This is the one 
that has been considered for inclusion in Emacs.)

To see this do

   emacs -Q
   C-x C-f javascript.el
   M-x eval-buffer
   C-x C-f my-large-javascript-file.js
   M-x javascript-mode

and then repeatedly press page down to scroll down. (Emacs will hang 
completely and use all CPU power available.)


In GNU Emacs 23.0.60.1 (i386-mingw-nt5.1.2600)
  of 2008-03-10

Note: I do not know which Emacs version jim-jam who told about the 
problem uses, but it must be at least Emacs 22.