Fast & Small Footprint
A lot of fairly common functionality has been omitted from the jQuery core library, and relegated to the realm of the plugin. Any additional required functionality can be included easily on a page-by-page basis to keep bandwidth and code bloat to a minimum. The jQuery core library is only about 24KB in size (Minified and Gzipped) so it is very easily to include in your application and very fast as well.
Short Learning curve & Great Documentation
The learning curve is short as you probably can start writing some jQuery code after a 30 minutes quick tutorial study. jQuery is also very well documented. You can find all the jQuery documentation at http://docs.jquery.com
Tons of Plugins
By including only a core set of features while providing a framework for extending the library, jQuery team made it easy to create plugins that you can reuse in all your jQuery projects, as well as share with other developers. A lot of people have taken advantage of jQuery’s extensibility, so there are already hundreds of excellent, downloadable plugins available from the jQuery plugin repository, with new ones added all the time.
CSS3 Selectors Compliant
jQuery fully supports the CSS3 selector specification. You can gain a head start on the future by learning and using CSS3 selectors right now in your production code.
One noteworthy utility is the supportsfunction, which tests to find certain features are available on the current user’s browser. Using the jQuery supports utility function, you can test to see if a certain feature is available to the user, and easily build applications that degrade gracefully on older browsers, or those not standards-compliant.
jQuery User Interface (jQuery UI ) separates out higher-level constructs and is packaged into a neat library that sits on top of jQuery. Accordions, sliders, dialog boxes, date pickers, and more—all ready to be used right now! You could spend a bunch of time creating them yourself in jQuery but the jQuery UI controls are configurable and sophisticated enough that your time would be better spent elsewhere.
Countless big players on the Web are jumping on the jQuery bandwagon: IBM, Netflix, Google (which both uses and hosts the jQuery library), and Microsoft, which now includes jQuery with its MVC framework and works with the open-source jQuery project to contribute new features to the jQuery library. With such a vast range of large companies on side, it’s a safe bet that jQuery will be around for some time to come—so the time and effort you invest in learning it will be well worth your while! jQuery’s popularity has also spawned a large and generous community that’s surprisingly helpful.