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

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.)

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.

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

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

Install the grunt-cli and bower packages if you haven't before. These should be done as global installs:

npm install -g grunt-cli bower

Make sure you have grunt and bower installed by testing:

grunt -version
bower -version

Enter the jquery directory and install the Node and Bower dependencies, this time without specifying a global(-g) install:

cd jquery && npm install

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

grunt

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:

• ajax: All AJAX functionality: $.ajax(), $.get(), $.post(), $.ajaxSetup(), .load(), transports, and ajax event shorthands such as .ajaxStart().
• ajax/xhr: The XMLHTTPRequest AJAX transport only.
• ajax/script: The <script> AJAX transport only; used to retrieve scripts.
• ajax/jsonp: The JSONP AJAX transport only; depends on the ajax/script transport.
• css: The .css() method plus non-animated .show(), .hide() and .toggle().
• deprecated: Methods documented as deprecated but not yet removed; currently only .andSelf().
• dimensions: The .width() and .height() methods, including inner- and outer- variations.
• effects: The .animate() method and its shorthands such as .slideUp() or .hide("slow").
• event-alias: All event attaching/triggering shorthands like .click() or .mouseover().
• offset: The .offset(), .position(), .offsetParent(), .scrollLeft(), and .scrollTop() methods.
• wrap: The .wrap(), .wrapAll(), .wrapInner(), and .unwrap() methods.
• sizzle: The Sizzle selector engine. When this module is excluded, it is replaced by a rudimentary selector engine based on the browser's querySelectorAll method that does not support jQuery selector extensions or enhanced semantics. See the selector-native.js file for details.

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:

npm install

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 and use the querySelectorAll-based selector engine:

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

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. The non-Sizzle selector engine currently does not pass unit tests because it is missing too much essential functionality.

Make sure you have the necessary dependencies:

bower install

Start grunt watch 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:

• Windows: WAMP download
• Mac: MAMP download
• Linux: Setting up LAMP
• Mongoose (most platforms)

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:

/path/to/special/location/jquery.js
/path/to/special/location/jquery.min.js

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.

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

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)

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:

• Ctrl + Alt + M - automerge as much as possible
• b - jump to next merge conflict
• s - change the order of the conflicted lines
• u - undo an merge
• left mouse button - mark a block to be the winner
• middle mouse button - mark a line to be the winner
• Ctrl + S - save
• Ctrl + Q - quit

expect( numAssertions );
stop();
start();

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

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] );

q( ... );

Example:

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

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

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

Example:

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

fireNative( node, eventType )

Example:

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

url( "some/url.php" );

Example:

url("data/test.html");

=> "data/test.html?10538358428943"


url("data/test.php?foo=bar");

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

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 );

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.