onbeforeunload Event
Example
Call a function when the page is about to be unloaded:
<body onbeforeunload="return myFunction()">
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Description
The onbeforeunload event occurs when a document is about to be unloaded.
This event allows you to display a message in a confirmation dialog box to inform the user whether he/she wants to stay or leave the current page.
The default message that appears in the confirmation box, is different in different browsers. However, the standard message is something like "Are you sure you want to leave this page?".
This message cannot be removed, unless you call preventDefault() on the event.
Syntax
In JavaScript, using the addEventListener() method:
object.addEventListener("beforeunload", myScript);
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Technical Details
| Bubbles: | No |
|---|---|
| Cancelable: | Yes |
| Event type: | UiEvent if generated from a user interface, Event otherwise |
| HTML tags: | <body> |
| DOM Version: | Level 2 Events |
Browser Support
onbeforeunload is a DOM Level 2 (2001) feature.
It is fully supported in all browsers:
| Chrome | Edge | Firefox | Safari | Opera | IE |
| Yes | Yes | Yes | Yes | Yes | 9-11 |
