BeforeUnloadEvent
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The BeforeUnloadEvent
interface represents the event object for the beforeunload
event, which is fired when the current window, contained document, and associated resources are about to be unloaded.
See the beforeunload
event reference for detailed guidance on using this event.
Instance properties
Inherits properties from its parent, Event
.
returnValue
Deprecated-
When set to a truthy value, triggers a browser-controlled confirmation dialog asking users to confirm if they want to leave the page when they try to close or reload it. This is a legacy feature, and best practice is to trigger the dialog by invoking
event.preventDefault()
, while also settingreturnValue
to support legacy cases.
Instance methods
Inherits methods from its parent, Event
.
Specifications
Specification |
---|
HTML Standard # the-beforeunloadevent-interface |
Browser compatibility
Report problems with this compatibility data on GitHubdesktop | mobile | server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
BeforeUnloadEvent | |||||||||||||
returnValue | |||||||||||||
User interaction required for dialog box |
Legend
Tip: you can click/tap on a cell for more information.
- Full support
- Full support
- Partial support
- Partial support
- No support
- No support
- Deprecated. Not for use in new websites.
- Has more compatibility info.
See also
beforeunload
event