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JavaScript: The Definitive Guide

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Window.onfocus() Handler

Name

Window.onfocus() Handler---invoked when window is given focus

Availability

Navigator 3.0

Synopsis

<BODY    a definition of the handler
    [ onFocus="JavaScript statements" ]
        ...
>
<FRAMESET    another way to define the handler
    [ onFocus="JavaScript statements" ]
       ...
>
window.onfocus=handler-func defining the handler directly
window.onfocus(); an explicit invocation of the handler

Description

onfocus() is an event handler invoked by the browser when a top-level browser window is given the input focus, either because the user has switched to the browser window, or because focus was transferred to the window with the Window focus() or blur() methods.

The onfocus() event handler can be defined in HTML by specifying the onFocus attribute of the <BODY> or <FRAMESET> tag of the document or frameset that occupies the top-level window. The value of this attribute may be any number of JavaScript statements, separated by semicolons. This event handler may also be defined by assigning a function to the onfocus property of the Window object.

Usage

If your web page does some sort of animation, you might use the onfocus() event handler to start the animation and the onblur() handler to stop it, so that it only runs while the user is paying attention to the window.

See Also

"Window", "Window.blur()", "Window.focus()", "Window.onblur()"


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