Chapter 1. Introduction to jQuery
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, jQuery is one of the most popular and widely used of these libraries.
Because it has become so widely used, web developers should be familiar with the jQuery library: 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 pocket reference form.
jQuery makes it easy to find the elements of a document, 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 document elements and then returns an object that represents those elements. This returned object provides many useful methods for operating on the matching elements as a group. Whenever possible, these methods return the object ...