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Chapter 13. Windows and Frames

Chapter 12 described the Window object and the central role it plays in client-side JavaScript. We've seen that the Window object serves as the global object for client-side JavaScript programs, and, as illustrated in Figure 12-1, it is also the root of the client-side object hierarchy.

Besides these special roles, the Window object is an important object in its own right. Every web browser window and every frame within every window is represented by a Window object. The Window object defines quite a few properties and methods that are important in client-side JavaScript programming. This chapter explores those properties and methods and demonstrates some important techniques for programming with windows and frames. Note that because the Window object is so central to client-side programming, this chapter is quite long. Don't feel you have to master all this material at once -- you may find it easier to study this chapter in several shorter chunks!

13.1. Window Overview

We begin this chapter with an overview of some of the most commonly used properties and methods of the Window object. Later sections of the chapter explain this material in more detail. As usual, the client-side reference section contains complete coverage of Window object properties and methods.

The most important properties of the Window object are the following:

A boolean value that is true only if the window has been closed.

defaultStatus, status
The text that appears in the status line of the browser.

A reference to the Document object that represents the HTML document displayed in the window. The Document object is covered in detail in Chapter 14.

An array of Window objects that represent the frames (if any) within the window.

A reference to the History object that represents the user's browsing history for the window.

A reference to the Location object that represents the URL of the document displayed in the window. Setting this property causes the browser to load a new document.

The name of the window. Can be used with the target attribute of the HTML <a> tag, for example.

A reference to the Window object that opened this one, or null if this window was opened by the user.

If the current window is a frame, a reference to the frame of the window that contains it.

A self-referential property; a reference to the current Window object. A synonym for window.

If the current window is a frame, a reference to the Window object of the top-level window that contains the frame. Note that top is different from parent for frames nested within other frames.

A self-referential property; a reference to the current Window object. A synonym for self.

The Window object also supports a number of important methods:

alert( ) , confirm( ), prompt( )
Display simple dialog boxes to the user and, for confirm( ) and prompt( ), get the user's response.

close( )
Close the window.

focus( ) , blur( )
Request or relinquish keyboard focus for the window. The focus( ) method also ensures that the window is visible by bringing it to the front of the stacking order.

moveBy( ) , moveTo( )
Move the window.

open( )
Open a new top-level window to display a specified URL with a specified set of features.

print( )
Print the window or frame -- same as if the user had selected the Print button from the window's toolbar (Netscape 4 and later and IE 5 and later only).

resizeBy( ) , resizeTo( )
Resize the window.

scrollBy( ) , scrollTo( )
Scroll the document displayed within the window.

setInterval( ) , clearInterval( )
Schedule or cancel a function to be repeatedly invoked with a specified delay between invocations.

setTimeout( ) , clearTimeout( )
Schedule or cancel a function to be invoked once after a specified number of milliseconds.

As you can see from these lists, the Window object provides quite a bit of functionality. The remainder of this chapter explores much of that functionality in more detail.

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