Introduction

In the previous chapter, we looked at the different examples of JavaScript runtime environments and had an overview of their components. We'll now look at one of those components in greater depth, that is, the Browser Object Model (BOM), and the APIs it exposes to JavaScript.

The BOM is a set of properties and methods that are made available to JavaScript by the browser. Now, you've come across many parts of the BOM already, with methods such as setTimeout(), and the document property, with its many methods, such as addEventListener(). It's a subtle but important point that the methods and properties we'll cover in this chapter are not part of the JavaScript programming language; that is to say, they're not part of the ECMAScript specification – the specification to which JavaScript engines are built – but they are methods and properties of the browser, and they form the interface between JavaScript and the browser (and by extension...