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:
Install the [grunt-cli](http://gruntjs.com/getting-started#installing-the-cli) and [bower](http://bower.io/) packages if you haven't before. These should be done as global installs:
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.
- **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.
For questions or requests regarding custom builds, please start a thread on the [Developing jQuery Core](https://forum.jquery.com/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.
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:
As the source code is handled by the version control system Git, it's useful to know some features used.
### cleaning ###
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):
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:
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