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:
- [Browser support](http://jquery.com/browser-support/) differs between the master (2.x) branch and the 1.x-master branch. Specifically, 2.x does not support legacy browsers such as IE6-8. The jQuery team continues to provide support for legacy browsers on the 1.x-master branch. Use the latest 1.x release if support for those browsers is required. See [browser support](http://jquery.com/browser-support/) for more info.
- To use jQuery in Node, browser extensions, and other non-browser environments, use only **2.x** releases. 1.x does not support these environments.
If you want create custom build or help with jQuery development, it would be better to install [grunt command line interface](https://github.com/gruntjs/grunt-cli) as a global package:
For example, an app that only used JSONP for `$.ajax()` and did not need to calculate offsets or positions of elements could exclude the offset and ajax/xhr modules.
Any module may be excluded except for `core`, and `selector`. To exclude a module, pass its path relative to the `src` folder (without the `.js` extension).
- **ajax**: All AJAX functionality: `$.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()`. Also removes **all** modules depending on css (including **effects**, **dimensions**, and **offset**).
- **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 removes jQuery.Callbacks. *Note* that modules that depend on jQuery.Deferred(AJAX, effects, core/ready) will not be removed and will still expect jQuery.Deferred to be there. Include your own jQuery.Deferred implementation or exclude those modules as well (`grunt custom:-deferred,-ajax,-effects,-core/ready`).
- **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.
As an option, 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. Simply set the `"amd"` option:
```bash
grunt custom --amd="custom-name"
```
Or, to define anonymously, set the name to an empty string.
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:
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 use 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