In celebration of jQuery’s 4th birthday, the jQuery team is pleased to release the latest major release of the jQuery JavaScript library! A lot of coding, testing, and documenting has gone into this release, and we’re really quite proud of it.
I want to personally thank Brandon Aaron, Ben Alman, Louis-Rémi Babe, Ariel Flesler, Paul Irish, Robert Katić, Yehuda Katz, Dave Methvin, Justin Meyer, Karl Swedberg, and Aaron Quint who put a lot of work into fixing bugs and getting the release out the door.
http://jquery14.com/day-01/jquery-14
Performance Overhaul of Popular Methods
Easy Setter Functions
Ajax
JSON and script types auto-detected by content-typeEtag support has been added
Strict JSON parsing, using native JSON.parse
Serialize HTML5 elements
Context for Ajax Request
Success callback receives XHR object as third argument
Explicitly set a content-type
Explicitly specify a JSONP callback name
Avoid pre-flighting cross-domain XHR
jQuery.ajax() is now using onreadystatechange instead of a timer