JavaScript: The Definitive Guide, 6th Edition

Chapter 19. The jQuery Library

JavaScript has an intentionally simple core API and an overly complicated client-side API that is marred by major incompatibilities between browsers. The arrival of IE9 eliminates the worst of those incompatibilities, but many programmers find it easier to write web applications using a JavaScript framework or utility library to simplify common tasks and hide the differences between browsers. At the time of this writing, one of the most popular and widely used such libraries is jQuery.^[47]

Because the jQuery library has become so widely used, web developers should be familiar with it: even if you don’t use it in your own code, you are likely to encounter it in code written by others. Fortunately, jQuery is stable and small enough to document in this book. You’ll find a comprehensive introduction in this chapter, and Part IV includes a jQuery quick reference. jQuery methods do not have individual entries in the reference section, but the jQuery gives a synopsis of each method.

jQuery makes it easy to find the elements of a document that you care about and then manipulate those elements by adding content, editing HTML attributes and CSS properties, defining event handlers, and performing animations. It also has Ajax utilities for dynamically making HTTP requests and general-purpose utility functions for working with objects and arrays.

As its name implies, the jQuery library is focused on queries. A typical query uses a CSS selector to identify a set of ...