Hi,

I am using M-; for commenting and uncommenting my code.  Recently, when I
was working on HTML page with JavaScript TAG, commenting the JavaScript
code is working but not the other way.  I posted it on Reddit
<https://www.reddit.com/r/emacs/comments/objna2/m_not_working_for_javascript_code/>
and one user told that it is a bug and post in emacs-devel mailing list.

He also suggested the below solution.

(defun fix-js-mode-comment-start-skip ()
  "newcomment.el expects comment delimiter text to begin at the
end of the first \\(...\\) pair in `comment-start-skip`."
  (setq comment-start-skip "\\(\\)\\(//+\\|/\\*+\\)\\s *"))

(with-eval-after-load 'js
  (add-hook 'js-mode-hook #'fix-js-mode-comment-start-skip))

regards,

sree