Sams Teach Yourself JavaScript in 24 Hours

Working with Web Documents

The document object represents a web document, or page. Web documents are displayed within browser windows, so it shouldn't surprise you to learn that the document object is a child of the window object.

Because the window object always represents the current window (the one containing the script), you can use window.document to refer to the current document. You can also simply refer to document, which automatically refers to the current window.

By the Way

You've already used the document.write method to display text within a web document. The examples in earlier hours only used a single window and document, so it was unnecessary to use window.document.writebut this longer syntax would have worked equally well.

If multiple windows or frames are in use, there might be several window objects, each with its own document object. To use one of these document objects, you use the name of the window and the name of the document.

In the following sections, you will look at some of the properties and methods of the document object that will be useful in your scripting.

Getting Information About the Document

Several properties of the document object include information about the current document in general:

document.URL specifies the document's URL. This is a simple text field. You can't change this property. If you need to send the user to a different location, use the window.location object, described later in this hour.
document.title lists the title of the current page, defined by the HTML <title> tag.
document.referrer is the URL of the page the user was viewing prior to the current pageusually, the page with a link to the current page.
document.lastModified is the date the document was last modified. This date is sent from the server along with the page.
document.bgColor and document.fgColor are the background and foreground (text) colors for the document, corresponding to the BGCOLOR and TEXT attributes of the <body> tag.
document.linkColor, document.alinkColor, and document.vlinkColor are the colors for links within the document. These correspond to the LINK, ALINK, and VLINK attributes of the <body> tag.
document.cookie enables you to read or set a cookie for the document. See http://www.jsworkshop.com/cookies.html for information about cookies.

As an example of a document property, Listing 4.1 shows a short HTML document that displays its last modified date using JavaScript.

Listing 4.1. Displaying the Last Modified Date

<html><head><title>Test Document</title></head> <body> <p>This page was last modified on: <script language="JavaScript" type="text/javascript"> document.write(document.lastModified); </script> </p> </body> </html>

This can tell the user when the page was last changed. If you use JavaScript, you don't have to remember to update the date each time you modify the page. (You could also use the script to always print the current date instead of the last modified date, but that would be cheating.)

By the Way

You might find that the document.lastModified property doesn't work on your web pages, or returns the wrong value. The date is received from the web server, and some servers do not maintain modification dates correctly.

Writing Text in a Document

The simplest document object methods are also the ones you will use most often. In fact, you've used one of them already. The document.write method prints text as part of the HTML page in a document window. This statement is used whenever you need to include output in a web page.

An alternative statement, document.writeln, also prints text, but it also includes a newline (\n) character at the end. This is handy when you want your text to be the last thing on the line.

Watch Out!

Bear in mind that the newline character is displayed as a space by the browser, except inside a <pre> container. You will need to use the <br> tag if you want an actual line break.

You can use these methods only within the body of the web page, so they will be executed when the page loads. You can't use these methods to add to a page that has already loaded without reloading it.

By the Way

You can also directly modify the text of a web page on newer browsers using the features of the new DOM. You'll learn these techniques in Hour 14.

The document.write method can be used within a <script> tag in the body of an HTML document. You can also use it in a function, provided you include a call to the function within the body of the document.

Using Links and Anchors

Another child of the document object is the link object. Actually, there can be multiple link objects in a document. Each one includes information about a link to another location or an anchor.

Did you Know?

Anchors are named places in an HTML document that can be jumped to directly. You define them with a tag like this: <a name="part2">. You can then link to them: <a href="#part2">.

You can access link objects with the links array. Each member of the array is one of the link objects in the current page. A property of the array, document.links.length, indicates the number of links in the page.

Each link object (or member of the links array) has a list of properties defining the URL. The href property contains the entire URL, and other properties define portions of it. These are the same properties as the location object, defined later in this hour.

You can refer to a property by indicating the link number and property name. For example, the following statement assigns the entire URL of the first link to the variable link1:

link1 = links[0].href;

The anchor objects are also children of the document object. Each anchor object represents an anchor in the current documenta particular location that can be jumped to directly.

Like links, you can access anchors with an array: anchors. Each element of this array is an anchor object. The document.anchors.length property gives you the number of elements in the anchors array.

Index: [SYMBOL][A][B][C][D][E][F][G][H][I][J][K][L][M][N][O][P][Q][R][S][T][U][V][W][X][Y]

Main Menu

	More Books
	PHP Hacks
	Processing Xml With Java - A Guide To Sax, Dom, Jdom, Jaxp, And Trax
	The Koran (Holy Qur'an)
	Macromedia Flash 8 Bible
	Search Engine Optimization for Dummies
	YouTube Traffic
	PHP 5 for Dummies
	Harry Potter and The Chamber of Secrets
	Harry Potter and the Sorcerer's Stone
	The Pilgrim's Progress
	Wireless Hacks
	Flash Hacks. 100 Industrial-Strength Tips & Tools
	PayPal Hacks. 100 Industrial-Strength Tips and Tools
	Amazon Hacks
	Pdf Hacks
	The Da Vinci Code
	Google Hacks
	The Holy Bible
	Windows XP For Dummies
	Harry Potter and the Half-Blood Prince
	Seo Book
	Upgrading and Repairing Networks
	Macromedia Dreamweaver 8 UNLEASHED
	Windows XP Annoyances
	Windows XP Hacks
	Microsoft Windows XP Power Toolkit
	Teach Yourself MS Office In 24Hours
	iPod & iTunes Missing Manual
	PC Hacks 100 Industrial-Strength Tips and Tools
	PC Overclocking, Optimization, and Tuning - 2th Edition
	PC Hardware In A Nutshell 3rd Edition
	PC Hardware in a Nutshell, 2nd Edition
	Upgrading and Repairing PCs
	Google for Dummies
	MySQL Cookbook
	Teach Yourself Macromedia Flash 8 In 24 Hours
	PHP CookBook
	Sams Teach Yourself JavaScript in 24 Hours
	PHP5 Manual

Free Games Paper Airplanes

500 Kostenlose Spiele