JavaScript: The Definitive Guide, Fourth Edition

Client-Side JavaScript

When a JavaScript interpreter is embedded in a web browser, the result is client-side JavaScript. This is by far the most common variant of JavaScript; when most people refer to JavaScript, they usually mean client-side JavaScript. This book documents client-side JavaScript, along with the core JavaScript language that client-side JavaScript incorporates.

We’ll discuss client-side JavaScript and its capabilities in much more detail later in this chapter. In brief, though, client-side JavaScript combines the scripting ability of a JavaScript interpreter with the document object model (DOM) defined by a web browser. These two distinct technologies combine in a synergistic way, so the result is greater than the sum of its parts: client-side JavaScript enables executable content to be distributed over the Web and is at the heart of a new generation of Dynamic HTML (DHTML) documents.

Just as the ECMA-262 specification defined a standard version of the core JavaScript language, the World Wide Web Consortium (W3C) has published a DOM specification (or recommendation) that standardizes the features a browser must support in its DOM. We’ll learn much more about this standard in Chapter 17, Chapter 18, and Chapter 19. Although the W3C DOM standard is not yet as well supported as it could be, it is supported well enough that web developers can start writing JavaScript code that relies on it.

Table 1-2 shows the core language version and DOM capabilities supported ...