JSHint.rb

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JSHint on Rails is a Ruby library which lets you run the JSHint JavaScript code checker on your Javascript code easily. JSHint on rails is a fork project from JSLint on Rails, adapted to work with jshint.

Requirements

  • Ruby 1.8.7 or 1.9.2+
  • Javascript engine compatible with execjs (on Mac and Windows it's provided by the OS)
  • JSON engine compatible with multi_json (included in Ruby 1.9, on 1.8 use e.g. json gem)
  • should work with (but doesn't require) Rails 2.x and 3.x

Installation

To use JSHint in Rails 3 you just need to do one thing:

  • add gem 'jshint-rb' to bundler's Gemfile

In Rails 2 and other frameworks JSHint on Rails can't be loaded automatically using a Railtie, so you have to load it explicitly. The procedure in this case is:

  • install the gem in your application using whatever technique is recommended for your framework (e.g. using bundler, or by installing the gem manually with gem install jshint-rb and loading it with require 'jshint')

  • in your Rakefile, add a line to load the JSHint tasks:

    require 'jshint/tasks'

Configuration

It's strongly recommended that you create your own copy of the JSHint config file provided by the gem and tweak it to suit your preferences. To create a new config file from the template in your config directory, call this rake task:

[bundle exec] rake jshint:copy_config

This will create a config file at config/jshint.yml listing all available options. If for some reason you'd like to put the config file at a different location, set the config_path variable somewhere in your Rakefile:

JSHint.config_path = "config/lint.yml"

There are two things you can change in the config file:

  • define which Javascript files are checked by default; you'll almost certainly want to change that, because the default is public/javascripts/**/*.js which means all Javascript files, and you probably don't want JSHint to check entire jQuery, Prototype or whatever other libraries you use - so change this so that only your scripts are checked (you can put multiple entries under "paths:" and "exclude_paths:")
  • enable or disable specific checks - I've set the defaults to what I believe is reasonable, but what's reasonable for me may not be reasonable for you

Running

To start the check, run the rake task:

[bundle exec] rake jshint

You will get a result like this (if everything goes well):

Running JSHint:

checking public/javascripts/Event.js... OK
checking public/javascripts/Map.js... OK
checking public/javascripts/Marker.js... OK
checking public/javascripts/Reports.js... OK

No JS errors found.

If anything is wrong, you will get something like this instead:

Running JSHint:

checking public/javascripts/Event.js... 2 errors:

Lint at line 24 character 15: Use '===' to compare with 'null'.
if (a == null && b == null) {

Lint at line 72 character 6: Extra comma.
},

checking public/javascripts/Marker.js... 1 error:

Lint at line 275 character 27: Missing radix parameter.
var x = parseInt(mapX);


Found 3 errors.
rake aborted!
JSHint test failed.

If you want to test specific file or files (just once, without modifying the config), you can pass paths to include and/or paths to exclude to the rake task:

rake jshint paths=public/javascripts/models/*.js,public/javascripts/lib/*.js exclude_paths=public/javascripts/lib/jquery.js

For the best effect, you should include JSHint check in your Continuous Integration build - that way you'll get immediate notification when you've committed JS code with errors.

Running from your code

If you would prefer to write your own rake task to run JSHint, you can create and execute the JSHint object manually:

require 'jshint'

lint = JSHint::Lint.new(
  :paths => ['public/javascripts/**/*.js'],
  :exclude_paths => ['public/javascripts/vendor/**/*.js'],
  :config_path => 'config/jslint.yml'
)

lint.run

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