Adding new features

The jQuery Core team receives many requests to add features to the library. Here are some of the criteria we use in our decisions on whether to add a feature:

• Does it require access to jQuery internals? If the feature needs information that only jQuery has, for example the list of events attached to an element, it is a candidate for feature addition.
• Can jQuery itself benefit from the feature? Features adding useful APIs that also improve the file size or performance inside jQuery itself are good candidates.
• Is the feature related to DOM operations? jQuery's primary mission is to be a DOM library. Features beyond that are often better served by libraries such as lodash for utilities or Raphaël for SVG.
• Is the need already served by a plugin? If there is a jQuery plugin that already does the job well, there is little reason for us to add duplicate functionality inside the library. Simply use the plugin.
• Does it change an existing API? Adding new flags or signatures to existing APIs can break code that duck-punches the API. New arguments also complicate documentation and can create confusing Boolean traps.
• Does it support best practice? jQuery wants to make it easy to write good and fast code, so new features should follow that pattern. jQuery 1.9 actually removed many features that lead to brittle or slow code.