JavaScript Document Object
In the JavaScript Window Object chapter we looked at how perform such tasks as opening and closing browser windows and controlling the appearance and position of those windows. Whilst the window object gives us the ability to control various aspects of the browser window it does not provide us any control over the content of the window. In order to manipulate the content that appears in the browser we need to turn to the JavaScript Document object.
What is the JavaScript Document Object?
The JavaScript Document object essentially contains the HTML elements that are contained the <head> and <body> sections of a web page. It provides the hooks (via a set of object methods and properties) that enable basic changes to be made to the content of a browser window from within a JavaScript script.
The Document object gets the initial value of its title property from the HTML <title> tag and a number of color and event values from the <body> element:
<body [alink="activated link color"] [background="background image file"] [bgcolor="background color"] [link="unvisited link color"] [onload="page load functionName"] [onunload="page unload functionName"] [text="foreground color"] [vlink="visited link color"]> </body>
It is important to note that these are only optional initial values. Regardless of whether these are declared in the <body> element they can still be set, or modified from JavaScript via the Document object.
JavaScript Document Object Methods and Properties
The JavaScript Document contains a wide range of methods and properties that are considerable use to developers. The following table lists the key methods and properties provided by the Document object:
Document Object Methods
| Method | Description |
|---|---|
| open() | Opens the output stream to the document for writing |
| close() | Closes the output stream to the document to prevent further writing |
| write() | Appends text to the document. |
| writeln() | Appends text to the document followed by a newline character |