Appendix A. jQuery Primer

A lot of libraries have been developed to make the DOM easier to work with, but few have the popularity and praise of jQuery. And for good reason: jQuery’s API is excellent and the library is lightweight and namespaced, so it shouldn’t conflict with anything else you’re using. What’s more, jQuery is easily extendable; a whole host of plug-ins have been developed, from JavaScript validation to progress bars.

jQuery is namespaced behind the jQuery variable, which is aliased with a dollar sign ($). Unlike libraries such as Prototype, jQuery doesn’t extend any native JavaScript objects, largely to avoid conflicts with other libraries.