JavaScript: The Definitive Guide, Fourth Edition

Chapter 14. The Document Object

Every Window object has a document property. This property refers to a Document object that represents the HTML document displayed in the window. The Document object is probably the most commonly used object in client-side JavaScript. We’ve already seen several examples in this book that use the write( ) method of the Document object to insert dynamic content into a document while it is being parsed. In addition to the frequently used write( ) method, the Document object defines properties that provide information about the document as a whole: its URL, its last-modified date, the URL of the document that linked to it, the colors in which it is displayed, and so on.

Client-side JavaScript exists to turn static HTML documents into interactive programs -- it is the Document object that gives JavaScript interactive access to the content of otherwise static documents. In addition to the properties that provide information about a document as a whole, the Document object has a number of very important properties that provide information about document content. The forms[] array, for instance, contains Form objects that represent all the HTML forms in the document. And the images[] and applets[] arrays contain objects that represent the images and applets in the document. These arrays and the objects they contain open up a world of possibilities for client-side JavaScript programs, and the bulk of this chapter is devoted to documenting them.

This chapter ...