PromiseRejectionEvent.promise

The PromiseRejectionEvent interface's promise read-only property indicates the JavaScript Promise which was rejected. You can examine the event's PromiseRejectionEvent.reason property to learn why the promise was rejected.

Syntax

promise = PromiseRejectionEvent.promise

Value

The JavaScript Promise which was rejected, and whose rejection went unhandled.

Examples

This example listens for unhandled promises and, if the reason is an object with a code field containing the text "Module not ready", it sets up an idle callback that will retry the task that failed to execute correctly.

event.preventDefault() is called to indicate that the promise has now been handled.

window.onunhandledrejection = function(event) {
  if (event.reason.code && event.reason.code == "Module not ready") {
    window.requestIdleCallback(function(deadline) {
      loadModule(event.reason.moduleName)
        .then(performStartup);
    });
    event.preventDefault();
  }
}

Specifications

Specification Status Comment
HTML Living Standard
The definition of 'PromiseRejectionEvent.promise' in that specification.
Living Standard Initial definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic supportChrome Full support 49Edge ? Firefox No support No
Notes Disabled
No support No
Notes Disabled
Notes Firefox doesn't yet send the unhandledrejection or understand rejectionhandled events. Completing the implementation will be addressed in bug 1362272.
Disabled This feature is behind the dom.promise_rejection_events.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.
IE No support NoOpera No support NoSafari No support NoWebView Android ? Chrome Android No support NoEdge Mobile ? Firefox Android No support No
Notes Disabled
No support No
Notes Disabled
Notes Firefox doesn't yet send the unhandledrejection or understand rejectionhandled events. Completing the implementation will be addressed in bug 1362272.
Disabled This feature is behind the dom.promise_rejection_events.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.
Opera Android No support NoSafari iOS No support NoSamsung Internet Android ?

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
See implementation notes.
See implementation notes.
User must explicitly enable this feature.
User must explicitly enable this feature.

See also

Document Tags and Contributors

Contributors to this page: fscholz, Sheppy, chrisdavidmills
Last updated by: fscholz,