This article introduces JavaScript frameworks in a clear, pragmatic and accessible way as well as weighing up pros and cons of each
http://coding.smashingmagazine.com/2012/07/27/journey-through-the-javascript-…
It’s a bit long, so probably not worth reading in detail unless you’re a hard core front end developer.
JavaScript frameworks have evolved considerably in the last few years and will support, and in many cases do better, many of the functions that developers find themselves creating over and over again. By using JavaScript frameworks such as JQuery and backbone.js developers are able to create a much richer user experience and more maintainable code.