Awesome

Sizzle

A pure-JavaScript CSS selector engine designed to be easily dropped in to a host library.

Contribution Guides

In the spirit of open source software development, jQuery always encourages community code contribution. To help you get started and before you jump into writing code, be sure to read these important contribution guidelines thoroughly:

What you need to build Sizzle

In order to build Sizzle, you need to have Node.js/npm latest and git 1.7 or later. (Earlier versions might work OK, but are not tested.)

For Windows you have to download and install git and Node.js.

Mac OS users should install Homebrew. Once Homebrew is installed, run brew install git to install git, and brew install node to install Node.js.

Linux/BSD users should use their appropriate package managers to install git and Node.js, or build from source if you swing that way. Easy-peasy.

How to build Sizzle

Clone a copy of the main Sizzle git repo by running:

git clone git://github.com/jquery/sizzle.git

In the sizzle/dist folder you will find build version of sizzle along with the minified copy and associated map file.

Testing

Run npm install, it's also preferable (but not necessarily) to globally install grunt-cli package – npm install -g grunt-cli
Open test/index.html in the browser. Or run npm test/grunt test on the command line, if environment variables BROWSER_STACK_USERNAME and BROWSER_STACK_ACCESS_KEY are set up, it will attempt to use Browserstack service (you will need to install java on your machine so browserstack could connect to your local server), otherwise PhantomJS will be used.
The actual unit tests are in the test/unit directory.

Developing with grunt

npm run build or grunt will lint, build, test, and compare the sizes of the built files.
npm start or grunt start can be run to re-lint, re-build, and re-test files as you change them.
grunt -help will show other available commands