Beginning JavaScript®, Fourth Edition

Chapter 6. Programming the Browser

Over the past few chapters, you've examined the core JavaScript language. You've seen how to work with variables and data, perform operations on those data, make decisions in your code, loop repeatedly over the same section of code, and even how to write your own functions. In the preceding chapter you moved on to learn how JavaScript is an object-based language, and you saw how to work with the native JavaScript objects. However, you are not interested only in the language itself; you want to find out how to write script for the web browser. Using this ability, you can start to create more impressive web pages.

Not only is JavaScript object-based, but the browser is also made up of objects. When JavaScript is running in the browser, you can access the browser's objects in exactly the same way that you used JavaScript's native objects in the last chapter. But what kinds of objects does the browser provide?

The browser makes available a remarkable number of objects. For example, there is a window object corresponding to the window of the browser. You have already been using two methods of this object, namely the alert() and prompt() methods. For simplicity, we previously referred to these as functions, but they are in fact methods of the browser's window object.

Another object made available by the browser is the page itself, represented by the document object. Again, you have already used methods and properties of this object. Recall from Chapter ...