In an announcement on the jQuery Blog, Timmy Willison explains the changes.
- jQuery.Deferred is now Promises/A+ compatible
- Added .catch() to Deferreds
- Error cases don’t silently fail
- Removed deprecated event aliases
- Animations now use requestAnimationFrame
- Massive speedups for some jQuery custom selectors
On top of the plethora of changes they’ve added a slim build, which excludes ajax, effects and deprecated code and comes in at about a fifth smaller.
Although jQuery is useful, some would call it overkill for certain tasks. jQuery is a 30k dependency, which isn’t a lot for a one-time load on a big website. If you’re using the Google CDN, there’s a chance it’ll already have been cached. Still, 30k is 30k, and that might be doubling the size of your web page, and that’s not even taking into account the performance hit of parsing jQuery.