Web/API/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 StandardThe definition of 'PromiseRejectionEvent.promise' in that specification.	Living Standard	Initial definition.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`promise`	Chrome Full support 49	Edge Full support ≤79	Firefox Full support 69 Full support 69 Full support 68 Disabled' Disabled' From version 68: 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 No	Opera Full support 36	Safari Full support 11	WebView Android Full support 49	Chrome Android Full support 49	Firefox Android Full support 68 Disabled' Full support 68 Disabled' Disabled' From version 68: 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 Full support 36	Safari iOS Full support 11.3	Samsung Internet Android Full support 5.0

Legend

Full support: Full support
No support: No support
User must explicitly enable this feature.': User must explicitly enable this feature.