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jQuery — New Wave JavaScript

Meetings are currently held on the platform.

Meeting minutes can be found at

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. Writing Code for jQuery Projects

References to issues/PRs

GitHub issues/PRs are usually referenced via gh-NUMBER, where NUMBER is the numerical ID of the issue/PR. You can find such an issue/PR under

jQuery has used a different bug tracker - based on Trac - in the past, available under It is being kept in read only mode so that referring to past discussions is possible. When jQuery source references one of those issues, it uses the pattern trac-NUMBER, where NUMBER is the numerical ID of the issue. You can find such an issue under

Environments in which to use jQuery

  • Browser support
  • jQuery also supports Node, browser extensions, and other non-browser environments.

What you need to build your own jQuery

To build jQuery, you need to have the latest Node.js/npm and git 1.7 or later. Earlier versions might work, but are not supported.

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

macOS 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 your own jQuery

First, clone the jQuery git repo.

Then, enter the jquery directory, install dependencies, and run the build script:

cd jquery
npm install
npm run build

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

Build all jQuery release files

To build all variants of jQuery, run the following command:

npm run build:all

This will create all of the variants that jQuery includes in a release, including jquery.js, jquery.slim.js, jquery.module.js, and jquery.slim.module.js along their associated minified files and sourcemaps.

jquery.module.js and jquery.slim.module.js are ECMAScript modules that export jQuery and $ as named exports are placed in the dist-module/ directory rather than the dist/ directory.

Building a Custom jQuery

The build script can be used to create a custom version of jQuery that includes only the modules you need.

Any module may be excluded except for core. When excluding selector, it is not removed but replaced with a small wrapper around native querySelectorAll (see below for more information).

Build Script Help

To see the full list of available options for the build script, run the following:

npm run build -- --help


To exclude a module, pass its path relative to the src folder (without the .js extension) to the --exclude option. When using the --include option, the default includes are dropped and a build is created with only those modules.

Some example modules that can be excluded or included 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. Also removes all modules depending on css (including effects, dimensions, and offset).

  • css/showHide: Non-animated .show(), .hide() and .toggle(); can be excluded if you use classes or explicit .css() calls to set the display property. Also removes the effects module.

  • deprecated: Methods documented as deprecated but not yet removed.

  • 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: The .on() and .off() methods and all event functionality.

  • event/trigger: The .trigger() and .triggerHandler() methods.

  • offset: The .offset(), .position(), .offsetParent(), .scrollLeft(), and .scrollTop() methods.

  • wrap: The .wrap(), .wrapAll(), .wrapInner(), and .unwrap() methods.

  • core/ready: Exclude the ready module if you place your scripts at the end of the body. Any ready callbacks bound with jQuery() will simply be called immediately. However, jQuery(document).ready() will not be a function and .on("ready", ...) or similar will not be triggered.

  • deferred: Exclude jQuery.Deferred. This also excludes all modules that rely on Deferred, including ajax, effects, and queue, but replaces core/ready with core/ready-no-deferred.

  • exports/global: Exclude the attachment of global jQuery variables ($ and jQuery) to the window.

  • exports/amd: Exclude the AMD definition.

  • selector: The full jQuery selector engine. When this module is excluded, it is replaced with 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.

Note: Excluding the full selector module will also exclude all jQuery selector extensions (such as effects/animatedSelector and css/hiddenVisibleSelectors).

AMD name

You can set the module name for jQuery's AMD definition. By default, it is set to "jquery", which plays nicely with plugins and third-party libraries, but there may be cases where you'd like to change this. Pass it to the --amd parameter:

npm run build -- --amd="custom-name"

Or, to define anonymously, leave the name blank.

npm run build -- --amd
File name and directory

The default name for the built jQuery file is jquery.js; it is placed under the dist/ directory. It's possible to change the file name using --filename and the directory using --dir. --dir is relative to the project root.

npm run build -- --slim --filename="jquery.slim.js" --dir="/tmp"

This would create a slim version of jQuery and place it under tmp/jquery.slim.js.

ECMAScript Module (ESM) mode

By default, jQuery generates a regular script JavaScript file. You can also generate an ECMAScript module exporting jQuery as the default export using the --esm parameter:

npm run build -- --filename=jquery.module.js --esm
Factory mode

By default, jQuery depends on a global window. For environments that don't have one, you can generate a factory build that exposes a function accepting window as a parameter that you can provide externally (see README of the published package for usage instructions). You can generate such a factory using the --factory parameter:

npm run build -- --filename=jquery.factory.js --factory

This option can be mixed with others like --esm or --slim:

npm run build -- --filename=jquery.factory.slim.module.js --factory --esm --slim --dir="/dist-module"

Custom Build Examples

Create a custom build using npm run build, listing the modules to be excluded. Excluding a top-level module also excludes its corresponding directory of modules.

Exclude all ajax functionality:

npm run build -- --exclude=ajax

Excluding css removes modules depending on CSS: effects, offset, dimensions.

npm run build -- --exclude=css

Exclude a bunch of modules (-e is an alias for --exclude):

npm run build -- -e ajax/jsonp -e css -e deprecated -e dimensions -e effects -e offset -e wrap

There is a special alias to generate a build with the same configuration as the official jQuery Slim build:

npm run build -- --filename=jquery.slim.js --slim

Or, to create the slim build as an esm module:

npm run build -- --filename=jquery.slim.module.js --slim --esm

Non-official custom builds are not regularly tested. Use them at your own risk.

Running the Unit Tests

Make sure you have the necessary dependencies:

npm install

Start npm start to auto-build jQuery as you work:

npm start

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:

Essential Git

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


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

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


For feature/topic branches, you should always use the --rebase flag to git pull, or if you are usually handling many temporary "to be in a github pull request" branches, run the 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.

The 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 a 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

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] );
throws( 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", "bar"]);

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" );



=> "data/index.html?10538358428943"


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

Run tests in an iframe

Some tests may require a document other than the standard test fixture, and these can be run in a separate iframe. The actual test code and assertions remain in jQuery's main test files; only the minimal test fixture markup and setup code should be placed in the iframe file.

testIframe( testName, fileName,
  function testCallback(
      assert, jQuery, window, document,
	  [ additional args ] ) {
  } );

This loads a page, constructing a url with fileName "./data/" + fileName. The iframed page determines when the callback occurs in the test by including the "/test/data/iframeTest.js" script and calling startIframeTest( [ additional args ] ) when appropriate. Often this will be after either document ready or window.onload fires.

The testCallback receives the QUnit assert object created by testIframe for this test, followed by the global jQuery, window, and document from the iframe. If the iframe code passes any arguments to startIframeTest, they follow the document argument.


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