jquery

jQuery: The Write Less, Do More, JavaScript Library

jQuery is a fast, concise, JavaScript Library that simplifies how you traverse HTML documents, handle events, perform animations, and add Ajax interactions to your web pages. jQuery is designed to change the way that you write JavaScript.

jQuery.com

There are quite a few javascript frameworks out there but jQuery is my favorite. Why? Because it is fast and concise. Plus it is very easy to understand and use. Plus there are all kinds of plugins available.