November 2001
Intermediate to advanced
936 pages
68h 43m
English
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Name
Window.onunload — the handler invoked when the browser leaves a page
Availability
JavaScript 1.0
Synopsis
<body onunload="handler" ... > <frameset onunload="handler" ... >window.onunload
Description
The onunload property of a Window specifies an
event handler function that is invoked when the browser
“unloads” a document or frameset in preparation for
loading a new one.
The
initial value of this property is a function that contains the
semicolon-separated JavaScript statements specified by the
onunload attribute of the
<body> or
<frameset> tags. The
onunload event handler provides the opportunity to
perform any necessary cleanup of the browser state before a new
document is loaded.
When the browser leaves a site using frames, the
onunload handler of the frameset is invoked before
the onunload handler for each of the frames. This
is the reverse of the order in which the onload
event handler is invoked.
The onunload( ) handler is invoked when the user
has instructed the browser to leave the current page and move
somewhere else. Therefore, it is usually inappropriate to delay the
loading of the desired new page by popping up dialog boxes (with
Window.confirm( ) or Window.prompt( ), for example) from an onunload event
handler.
See Also
Window.onload; Chapter 19; Event, EventListener, and EventTarget in the DOM reference section
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.