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AvailabilityJavaScript 1.0 Synopsis<body onunload="handler" ... > <frameset onunload="handler" ... > window.onunload DescriptionThe 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 AlsoWindow.onload; Chapter 19; Event, EventListener, and EventTarget in the DOM reference section |
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