jQuery - New Wave JavaScript

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:

  1. Getting Involved
  2. Core Style Guide
  3. Tips For Bug Patching

What you need to build your own jQuery

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

Windows users have two options:

  1. Install msysgit (Full installer for official Git) and a binary version of Node.js. Make sure all two packages are installed to the same location (by default, this is C:\Program Files\Git).
  2. Install Cygwin (make sure you install the git and which packages), and a binary version of Node.js.

Mac OS users should install Xcode (comes on your Mac OS install DVD, or downloadable from Apple’s Xcode site) and 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 your own jQuery

First, clone a copy of the main jQuery git repo by running:

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

Install the grunt-cli package so that you will have the correct version of grunt available from any project that needs it. This should be done as a global install:

npm install -g grunt-cli

Enter the jquery directory and install the Node dependencies, this time without specifying a global install:

cd jquery && npm install

Make sure you have grunt installed by testing:

grunt -version

Then, to get a complete, minified (w/ Uglify.js), linted (w/ JSHint) version of jQuery, type the following:


The built version of jQuery will be put in the dist/ subdirectory, along with the minified copy and associated map file.


Special builds can be created that exclude subsets of jQuery functionality. This allows for smaller custom builds when the builder is certain that those parts of jQuery are not being used. For example, an app that only used JSONP for $.ajax() and did not need to calculate offsets or positions of elements could exclude the offset and ajax/xhr modules. The current modules that can be excluded are:

The grunt build process is aware of dependencies across modules. If you explicitly remove a module, its dependent modules will be removed as well. For example, excluding the css module also excludes effects, since the effects module uses .css() to animate CSS properties. These dependencies are listed in Gruntfile.js and the build process shows a message for each dependent module it excludes.

To create a custom build of the latest stable version, first check out the version:

git pull; git checkout $(git describe --abbrev=0 --tags)

Then, make sure all Node dependencies are installed and all Git submodules are checked out:

npm install && grunt

Create the custom build, use the grunt custom option, listing the modules to be excluded. Examples:

Exclude all ajax functionality:

grunt custom:-ajax

Exclude css, effects, offset, dimensions, and position. Excluding css automatically excludes its dependent modules:

grunt custom:-css,-position

Exclude all optional modules:

grunt custom:-ajax,-css,-deprecated,-dimensions,-effects,-event-alias,-offset,-wrap

For questions or requests regarding custom builds, please start a thread on the Developing jQuery Core section of the forum. Due to the combinatorics and custom nature of these builds, they are not regularly tested in jQuery’s unit test process.

Running the Unit Tests

Start grunt to auto-build jQuery as you work:

cd jquery && grunt watch

Run the unit tests with a local server that supports PHP. Ensure that you run the site from the root directory, not the “test” directory. No database is required. Pre-configured php local servers are available for Windows and Mac. Here are some options:

Building to a different directory

To copy the built jQuery files from /dist to another directory:

grunt && grunt dist:/path/to/special/location/

With this example, the output files would be:


To add a permanent copy destination, create a file in dist/ called “.destination.json”. Inside the file, paste and customize the following:

  "/Absolute/path/to/other/destination": true

Additionally, both methods can be combined.

Updating Submodules

Update the submodules to what is probably the latest upstream code.

grunt update_submodules

Note: This task will also be run any time the default grunt command is used.

Essential Git

As the source code is handled by the version control system Git, it’s useful to know some features used.


The repository uses submodules, which normally are handled directly by the grunt update_submodules command, but sometimes you want to be able to work with them manually.

Following are the steps to manually get the submodules:

git clone https://github.com/jquery/jquery.git
cd jquery
git submodule init
git submodule update


git clone https://github.com/jquery/jquery.git
cd jquery
git submodule update --init


git clone --recursive https://github.com/jquery/jquery.git
cd jquery

If you want to work inside a submodule, it is possible, but first you need to checkout a branch:

cd src/sizzle
git checkout master

After you’ve committed your changes to the submodule, you’ll update the jquery project to point to the new commit, but remember to push the submodule changes before pushing the new jquery commit:

cd src/sizzle
git push origin master
cd ..
git add src/sizzle
git commit


If you want to purge your working directory back to the status of upstream, following commands can be used (remember everything you’ve worked on is gone after these):

git reset --hard upstream/master
git clean -fdx


For feature/topic branches, you should always used the --rebase flag to git pull, or if you are usually handling many temporary “to be in a github pull request” branches, run following to automate this:

git config branch.autosetuprebase local

(see man git-config for more information)

handling merge conflicts

If you’re getting merge conflicts when merging, instead of editing the conflicted files manually, you can use the feature git mergetool. Even though the default tool xxdiff looks awful/old, it’s rather useful.

Following are some commands that can be used there:

QUnit Reference

Test methods

expect( numAssertions );

note: QUnit’s eventual addition of an argument to stop/start is ignored in this test suite so that start and stop can be passed as callbacks without worrying about their parameters

Test assertions

ok( value, [message] );
equal( actual, expected, [message] );
notEqual( actual, expected, [message] );
deepEqual( actual, expected, [message] );
notDeepEqual( actual, expected, [message] );
strictEqual( actual, expected, [message] );
notStrictEqual( actual, expected, [message] );
raises( block, [expected], [message] );

Test Suite Convenience Methods Reference (See test/data/testinit.js)

Returns an array of elements with the given IDs

q( ... );


q("main", "foo", "bar");

=> [ div#main, span#foo, input#bar ]

Asserts that a selection matches the given IDs

t( testName, selector, [ "array", "of", "ids" ] );


t("Check for something", "//[a]", ["foo", "baar"]);

Fires a native DOM event without going through jQuery

fireNative( node, eventType )


fireNative( jQuery("#elem")[0], "click" );

Add random number to url to stop caching

url( "some/url.php" );



=> "data/test.html?10538358428943"


=> "data/test.php?foo=bar&10538358345554"

Load tests in an iframe

Loads a given page constructing a url with fileName: "./data/" + fileName + ".html" and fires the given callback on jQuery ready (using the jQuery loading from that page) and passes the iFrame’s jQuery to the callback.

testIframe( fileName, testName, callback );

Callback arguments:

callback( jQueryFromIFrame, iFrameWindow, iFrameDocument );

Load tests in an iframe (window.iframeCallback)

Loads a given page constructing a url with fileName: "./data/" + fileName + ".html" The given callback is fired when window.iframeCallback is called by the page The arguments passed to the callback are the same as the arguments passed to window.iframeCallback, whatever that may be

testIframeWithCallback( testName, fileName, callback );


If you have any questions, please feel free to ask on the Developing jQuery Core forum or in #jquery on irc.freenode.net.