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.
General info
- Specification
- HTML5
- Interface
- Event
- Bubbles
- No
- Cancelable
- Yes
- Target
- defaultView
- Default Action
- Varies (prompts the user for confirmation to leave the page).
Properties
{{OpenEventProperties()}}{{EventProperties()}}{{CloseEventProperties()}}
Example
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. });
Related Events
{{LoadRelatedEvents()}}
Reference