Web/API/PromiseRejectionEvent/PromiseRejectionEvent

The PromiseRejectionEvent() constructor returns a newly created PromiseRejectionEvent, which represents events fired when a JavaScript Promise is rejected. With promise rejection events, it becomes possible to detect and report promises which fail and whose failures go unnoticed. It also becomes easier to write a global handler for errors.

There are two types of PromiseRejectionEvent: unhandledrejection is sent by the JavaScript runtime when a promise is rejected but the rejection goes unhandled. A rejectionhandled event is emitted if a promise is rejected but the rejection is caught by a rejection handler..

Syntax

promiseRejectionEvent = PromiseRejectionEvent(type, options);

Parameters

The PromiseRejectionEvent() constructor also inherits parameters from Event().

type: A string representing the name of the type of the PromiseRejectionEvent. This is case-sensitive and should be one of "rejectionhandled" or "unhandledrejection", to match the event names of the possible (non-synthetic) PromiseRejectionEvent events that user agents can actually fire).
options: An Object specifying details about the rejection which occurred:

promise The Promise that was rejected. reason Any value or Object which represents the reason the promise was rejected. This can be anything from a numeric error code to an error DOMString to an object which contains detailed information describing the situation resulting in the promise being rejected.

Return value

A new PromiseRejectionEvent configured as specified by the parameters.

Examples

This example creates a new unhandledrejection event for the promise myPromise with the reason being the string "My house is on fire". The reason could just as easily be a number, or even an object with detailed information including the home address, how serious the fire is, and the phone number of an emergency contact who should be notified.

let myRejectionEvent = new PromiseRejectionEvent("unhandledrejection", {
  promise : myPromise,
  reason : "My house is on fire"
});

Specifications

Specification	Status	Comment
HTML Living StandardThe definition of 'the PromiseRejectionEvent interface' 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
`PromiseRejectionEvent()` constructor	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.