Why linting Javascript is totally bloody useless

There was a post this week that was talked about how a missing “var” ruined their launch (because it put the Javascript variable in the global/module scope). All of the discussion about this seemed to focus on one thing “You Should Have Run jslint”.

I’m here to tell you that jslint (and the fork: jshint) is absolutely bloody useless, and hence I don’t use it.

Let’s have a quick look shall we. First let’s install jshint (which is better than jslint, and more modern):

$ sudo npm -g install jshint
Password:
/usr/local/bin/jshint -> /usr/local/lib/node_modules/jshint/bin/hint
jshint@0.5.2 /usr/local/lib/node_modules/jshint 
├── argsparser@0.0.6
└── minimatch@0.0.4

That all went well… So lets try it on haraka.js:

$ jshint haraka.js 
haraka.js: line 3, col 1, Use the function form of "use strict".
haraka.js: line 5, col 14, 'require' is not defined.
haraka.js: line 8, col 1, 'process' is not defined.
haraka.js: line 8, col 22, 'process' is not defined.
haraka.js: line 10, col 5, 'require' is not defined.
haraka.js: line 10, col 34, 'process' is not defined.
haraka.js: line 13, col 5, 'process' is not defined.
haraka.js: line 13, col 46, 'process' is not defined.
haraka.js: line 16, col 14, 'require' is not defined.
haraka.js: line 17, col 14, 'require' is not defined.
haraka.js: line 18, col 14, 'require' is not defined.
haraka.js: line 20, col 1, 'exports' is not defined.
haraka.js: line 21, col 35, '__dirname' is not defined.
haraka.js: line 24, col 1, 'process' is not defined.
haraka.js: line 34, col 5, 'process' is not defined.
haraka.js: line 37, col 52, 'exports' is not defined.

16 errors

WTF? This script is pretty battle tested. Everything it has complained about are node.js variables, but everything I have read told me that jshint was node.js compatible.

So maybe jshint just shouldn’t be used. Let’s do a search on NPM for alternatives:

lint                  This package provide lint validation library + node-lint command line tool allows you to che

Looks promising. Installed it, tried it:

$ node-lint haraka.js 

node.js:134
        throw e; // process.nextTick error, or 'error' event on first tick
        ^
Error: Cannot find module 'vows'
    at Function._resolveFilename (module.js:320:11)
    at Function._load (module.js:266:25)
    at require (module.js:348:19)
    at Object.<anonymous> (/usr/local/lib/node_modules/lint/lib/lint/vows.js:5:12)
    at Module._compile (module.js:404:26)
    at Object..js (module.js:410:10)
    at Module.load (module.js:336:31)
    at Function._load (module.js:297:12)
    at require (module.js:348:19)
    at Object.<anonymous> (/usr/local/lib/node_modules/lint/lib/lint/index.js:15:16)

Fucking useless. And dependencies really aren’t that hard in npm. Let’s press on:

nodelint              The nodelint command line tool allows you to check for problems using JSLint. You can specif

What do we get:

$ nodelint haraka.js 
0 errors

Praise Thor! OK so now we’re getting somewhere. Let’s move on to another file:

$ nodelint utils.js 
utils.js, line 5, character 78: Use the array literal notation [].
var CHARS = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'.split('');
utils.js, line 9, character 10: Move 'var' declarations to the top of the function.
for (var i = 0; i < 36; i++) {
utils.js, line 9, character 10: Stopping.  (10% scanned).

3 errors

These kinds of errors are completely fucking unreasonable, and laid down by Crockford who clearly needs to revise his viewpoint – putting the var in the for() statement is a reasonable thing to do, and yes I KNOW it doesn’t do what it looks like it does. I don’t care. And the problem is that these aren’t configurable checks for jslint – the “var at the top of the function” is not a parameter in the jslint config, and if it finds too many of those it just stops until you fix them!

So does nodelint actually find anything worth worrying about?

The truth is, yes it does occasionally find some issues, but getting it to accept your style is hard. Getting it to find real bugs is really hard. I’d love to be proved otherwise.