Version History of jQuery 1.4.min
Performance Overhaul of Popular Methods
Many of the most popular and commonly used jQuery methods have seen a significant rewrite in jQuery 1.4. When analyzing the code base we found that we were able to make some significant performance gains by comparing jQuery against itself: Seeing how many internal function calls were being made and to work to reduce the complexity of the code base.
In jQuery 1.4 we’ve significantly reduced the complexity of the most popular methods in jQuery. The full performance details can be found below.
There are so many changes that we have decided that rather than posting it here on OldApps, you’d be better off taking a look at it on their change log page: http://jquery14.com/day-01/jquery-14