Many developers have come to rely on jQuery to ease some of the headaches of developing sophisticated, cross-browser web UIs, particularly where it comes to supporting the quirks of older browsers – IE being the worst of the lot.
By some counts, jQuery is now used on more than 50 per cent of all websites, making it much more popular than competing frameworks such as Dojo, MooTools, Prototype, or the YUI Library.
Beginning with jQuery 2.0, however, developers who want to support the oldest versions of IE will also need to use an older version of the jQuery library.
"jQuery 2.0 is intended for the modern web; we've got jQuery 1.x to handle older browsers and fully expect to support it for several more years," the project's Dave Methvin said in release notes posted to the jQuery Foundation website on Thursday.
By removing the code required to support these legacy browsers, Methvin said, the project's developers have managed to reduce the size of the library's code base by 12 per cent while improving its performance at the same time.
Methvin said the library is also now more suitable for applications where compatibility with older browsers isn't necessary, and where the code needed for old-IE compatibility can often cause problems of its own.
Examples of such applications include Chrome extensions and apps, Windows Store apps for Windows 8, node.js applications, and web standards–based mobile apps created using tools like PhoneGap/Cordova.
In fact, Methvin said, the jQuery developers might have liked to have removed more code that would have improved performance further, but doing so would have broken compatibility with browsers on mobile devices running Android 2.x "Gingerbread."
"Android/WebKit 2.x browsers are now the weakest link," Methvin wrote. "We're carefully watching Android 2.x market share to determine when we can cross it off the support list, and don't expect it to take very long."
Web developers who still need to support IE 6, 7, or 8 should continue to use the 1.x branch of jQuery, which is still being maintained. That branch is currently on version 1.9 and will be upgraded to 1.10 within a few months.
The jQuery 2.0 library is API-compatible with jQuery 1.9, and the project's developers say they plan to maintain feature parity between the two branches – so 1.10 will correspond to 2.0, 1.11 will correspond to 2.1, and so on.
Because of this, it's probably a good idea to start upgrading existing jQuery sites to version 1.9 now, to avoid additional pain later. The project's maintainers have posted an upgrade guide to help developers complete the transition, in addition to a jQuery Migrate plugin that can identify code that uses deprecated APIs and features.
Developers can download any of jQuery 1.x, jQuery 2.x, or the jQuery Migrate plugin from the project's official website. ®