Our volunteers haven't translated this article into ไทย yet. Join us and help get the job done!
The beforeunload event is fired when the window, the document and its resources are about to be unloaded.
When a non-empty string is assigned to the returnValue Event property, a dialog box appears, asking the users for confirmation to leave the page (see example below). When no value is provided, the event is processed silently.
| Bubbles | No |
| Cancelable | Yes |
| Target objects | defaultView |
| Interface | Event |
Examples
window.addEventListener("beforeunload", function( event ) {
event.returnValue = "\o/";
});
//is equivalent to
window.addEventListener("beforeunload", function( event ) {
event.preventDefault();
});
Webkit-based browsers don't follow the spec for the dialog box. An almost cross-browser working example would be close to the below example.
window.addEventListener("beforeunload", function (e) {
var confirmationMessage = "\o/";
(e || window.event).returnValue = confirmationMessage; //Gecko + IE
return confirmationMessage; //Webkit, Safari, Chrome etc.
});