If you edit the JavaScript files under Emacs, it is recommanded that
you add the following to your .emacs:

(setq auto-mode-alist 
      (append '(("\\.js" . java-mode))
              auto-mode-alist))

This will switch to Java mode, that works quite well for JavaScript
files, whenever you load a .js file.

Make sure all files stay in UTF-8. This is needed for
internationalization and ease of maintaince.