jQuery 3.0 supports modern browsers and environments from IE9 forward. The 3.0 release is not a major rework of the jQuery codebase, but it supports the library’s shift to semantic versioning and adds several new features including simplified “.show()” and “.hide()” methods, a controversial change jQuery core team member Timmy Willison said will break some code. But ultimately, he said, the features will solve the larger problem of special cases and checks by reverting to a “simple, primordial model.”
(Related: Dave Methvin talks jQuery 3.0 and the future of Web development)
The release also updates the jQuery “.data()” implementation to more closely match the HTML5 dataset specification; adds Promises/A+ compatibility for ECMAScript 2015 Promises in “jQuery.Deferred”; removes special-case Deferred methods in “jQuery.ajax”; and prevents error cases from silently failing, among other feature and performance improvements.
jQuery Compat 3.0 is the manifestation of jQuery’s realigned browser support policies, with the latest release supporting legacy browsers such as IE8.