Merge pull request #19219 from twbs/contrib-jq-event-aliases

CONTRIBUTING: Document restriction regarding jQuery event alias methods

CONTRIBUTING.md

@@ -235,6 +235,7 @@ includes code changes) and under the terms of the
 - 2 spaces (no tabs)
 - strict mode
 - "Attractive"
+- Don't use [jQuery event alias convenience methods](https://github.com/jquery/jquery/blob/master/src/event/alias.js) (such as `$().focus()`). Instead, use [`$().trigger(eventType, ...)`](http://api.jquery.com/trigger/) or [`$().on(eventType, ...)`](http://api.jquery.com/on/), depending on whether you're firing an event or listening for an event. (For example, `$().trigger('focus')` or `$().on('focus', function (event) { /* handle focus event */ })`) We do this to be compatible with custom builds of jQuery where the event aliases module has been excluded.
 
 ### Checking coding style