jQuery 4.0.0 JavaScript library features trusted types

Version 4.0.0 of the still-widely-used jQuery JavaScript library is now available. Celebrated as the first major release in nearly 10 years, jQuery 4.0.0 features support for trusted types and a new, slimmer build.

Announced January 17, the newest version of the jQuery JavaScript library can be downloaded from jquery.com.  Trusted types in jQuery 4.0.0 ensure that HTML in the TrustedHTML interface can be input to jQuery manipulation methods in compliance with a browser’s Content Security Policy (CSP) required-trusted-types-for directive. In addition, while some AJAX requests already were using <script> tags to maintain attributes such as crossdomain, jQuery’s builders have switched most asynchronous script requests to use <script> tags to avoid any CSP errors caused by inline scripts. There still are a few cases where XHR is used for asynchronous script requests, such as when the "headers" option is passed, but <script> tag is used whenever possible.

jQuery 4.0.0 also debuts with a slimmer build, with the removal of deferred objects and callbacks. Deferreds have long-supported the Promises A+ standard for interoperable JavaScript promises; however, in most cases, native promises, available in all jQuery-supported browsers but IE 11, can be used. And while deferred objects have some extra features that native promises do not support, most usage can be migrated to Promise methods, according to the announcement. For developers who must support IE 11, it is best to use the main build or add a polyfill for native promises. IE 10 and older versions are not supported in jQuery 4.0.0.

Now 20 years old, jQuery is still used by 70.9% of all websites, according to web technology surveyor W3Techs. Now under the jurisdiction of the OpenJS Foundation, jQuery is intended to simplify capabilities such as HTML document traversal and manipulation, event handling, and animation via an API that works across a multitude of browsers. Other highlights of jQuery 4.0.0 include the following:

• Focus event order now follows the World Wide Web Consortium (W3C) specification, bringing jQuery in line with the event order supported in the latest versions of most browsers. This event order differs from the order used in older versions of jQuery, making it a breaking change. Starting with jQuery 4.0.0, the library no longer supports override native behavior, and will follow the current W3C specification: blur, focusout, focus, focusin.
• Internal-only methods were removed from the jQuery prototype. This prototype had Array methods that did not behave like other jQuery methods and were intended only for internal use. Developers who were using the removed push, sort, and splice methods can replace $elems.push( elem ) with [].push.call( $elems, elem ).
• With the release of jQuery 4.0.0, jQuery 3.x now will receive only critical updates.