js2-mode

The improved js-mode in 27.x is definitely worth checking out, especially if you use React/JSX. Had many issues wrestling with indentation in previous setup. https://github.com/mooz/js2-mode/blob/master/README.md#react...

The issue tracker for js2-mode illustrates that such a parsing approach is no guarantee of real-world accuracy either. https://github.com/mooz/js2-mode/issues The goal just shifts from having a semi-accurate regexp tokenizer, to having the language mode's complex parser match the complex parser of the language it targets—which will pretty much never happen, unless the language is exquisitely simple, like maybe restricted dialects of Scheme... or Brainfuck.

> I've never used a language mode that worked properly in all cases. You need a full parser for that to happen, most mode authors don't bother[0]. JS2-mode (https://github.com/mooz/js2-mode/) does that (or attempts to). Most syntactic colorisers are souped-up tokenisers, not actual parsers. It suffices in 99% of cases, but breaks badly elsewhere. [0] it would help if more languages made fast parsing machinery externally available as a convenient API. ALAS, that's rarely the case, even less so for fast parsing machinery which doesn't throw the information you need for syntactic coloration out the window.

Yes, tit the default mode is through regexs, and most of the modes use it. But I think the OP's point was you are not limited by it, besides semantic (which I haven't never bothered to setup, there is js2-mode[0] as examples of modes that don't use regexps to operate on the language. There is even js2-refactor[1] built on top of it. You can read about js2-mode origin story here[2], and you would see that lack of threads in elisp hindered its development. [0]: https://github.com/mooz/js2-mode [1]: https://github.com/magnars/js2-refactor.el [2]: http://steve-yegge.blogspot.com/2008/03/js2-mode-new-javascr...

emacs js2-mode uses recursive-descent parser to build up js ast with full recognition of Ecma-262 language standard and exposes ast for use in other pugins https://github.com/mooz/js2-mode/blob/master/js2-mode.el 11k amazing loc

Yeah. My favorite example is JS-2 mode[1]. It's a brilliant mode for editing JavaScript released by Steve Yegge. However, it had some shortcomings and (minor) bugs; Yegge did not have time to support it any more. [1]: http://code.google.com/p/js2-mode/ Then somebody cloned it on GitHub[2], changed the indentation, fixed some bugs and added some features. In the past, using JS-2 mode was a bit of a compromise--intelligence at the cost of weird behavior. Now there is no compromise at all. [2]: https://github.com/mooz/js2-mode

Like dangrossman said, use console.log. Check out these videos from Paul Irish on using console effectively: http://www.youtube.com/watch?v=4mf_yNLlgic http://www.youtube.com/watch?v=nOEw9iiopwI Since you are an emacs user, you may want to try mooz's community fork of Yegge's js2-mode https://github.com/mooz/js2-mode Haven't tried it myself, but you may also want to look at Moz Repl in emacs. http://www.emacswiki.org/emacs/MozRepl Finally, check out Christian Johansen's and Magnar Sveens .emacs.d for some ideas on how to set up your emacs for javascript. https://github.com/magnars/.emacs.d https://github.com/cjohansen/.emacs.d For TDD, you 3 main options worth checking out are: Buster.js looks really promising and does both server-side and client-side testing. If you don't like buster.js for whatever reason, Mocha is a popular node.js ser

JS2-mode for Emacs[1][2] does this. It is awesome. [1]: Original version: http://code.google.com/p/js2-mode/ [2]: Improved (IMO) fork: https://github.com/mooz/js2-mode Additionally, you can configure JS[HL]int to use flymake[3]. The trick is to improve performance by having it talk to a running JavaScript process (e.g. a node server) instead of starting a new one each time. [3]: http://www.emacswiki.org/emacs/FlymakeJavaScript#toc3

The fork of js2-mode at https://github.com/mooz/js2-mode will catch that, as will js3-mode.

Since everyone is chiming in with ways to prevent this sort of thing, here is another: js2 mode for Emacs[1]. This is a mode originally written by Steve Yegge and then modified by some other people (be sure to get that version) that actually parses the code and, among other things, highlights global variables in a different color than local ones. I find this, along with the other things js2 does, helps prevent a whole host of annoying JavaScript issues, as I type. [1]: https://github.com/mooz/js2-mode