Fires prior to a page being unloaded.
| Inline |
<element onbeforeunload = "handler" ... > |
| Script |
object.onbeforeunload = handler |
JScript® (compatible with ECMA-262 language specification) only |
| Bubbles |
No |
| Cancels |
No |
| To invoke |
- Close the current browser window.
- Navigate to another location by entering a new address or selecting a Favorite.
- Click the Back, Forward, Refresh, or Home button.
- Click on an anchor that refers the browser to another Web page.
- Invoke the anchor click method.
- Invoke the document write method.
- Invoke the document open method.
- Invoke the document close method.
- Invoke the window close method.
- Invoke the window open method, providing the possible value _self for the window name.
- Invoke the window navigate or NavigateAndFind method.
- Invoke the location replace method.
- Invoke the location reload method.
- Specify a new value for the location href property.
- Submit a FORM to the address specified in the ACTION attribute via the INPUT_submit control, or invoke the form submit method.
|
| Default action |
Signals that the page is about to be unloaded. |
This event gives the programmer a chance to request that the user not leave the page. When a string is returned to this event, a dialog box displays that gives the user the option of staying on the page. The returned string displays in a predefined area.
<script language="JavaScript">
function Window_beforeUnload() {
alert("Window is unloading");
event.returnValue =
"Click cancel to stay on this page.";
}
</script>
While event handlers in the Document Object Model do not receive parameters directly, the handler can query the event object for data.
Event Object Properties
| altKey |
Retrieves the current state of the ALT key. |
| clientX |
Retrieves the x-coordinate of the position of the cursor when the mouse is clicked, relative to the size of the client area of the window but excluding window decorations or scroll bars. |
| clientY |
Returns the y-coordinate of the position of the cursor when the mouse is clicked, relative to the size of the client area of the window but excluding window decorations or scroll bars. |
| ctrlKey |
Retrieves the state of the CTRL key. |
| returnValue |
Sets or retrieves the return value from the event. |
| shiftKey |
Retrieves the state of the SHIFT key. |
| type |
Retrieves the event name from the event object. |
The following example shows use of the onbeforeunload event.
Sample Code
<html>
<head>
<script language="JavaScript">
function closeIt() {
event.returnValue = "Any string value here
will force a dialog box to appear
before closing the window.";
}
</script>
</head>
<body onbeforeunload="closeIt()">
<p>Navigate to another page
to fire the before unload event.
</body>
</html>
FRAMESET, window
onload, onunload