PromiseRejectionEvent

The PromiseRejectionEvent interface represents events which are fired when JavaScript Promises are rejected. These events are particularly useful for telemetry and debugging purposes.

Constructor

PromiseRejectionEvent()

Creates a PromiseRejectionEvent event with the given parameters.

Properties

Also inherits properties from its parent Event.

PromiseRejectionEvent.promise Read only

The JavaScript Promise that was rejected.

PromiseRejectionEvent.reason Read only

A value or Object indicating why the promise was rejected, as passed to Promise.reject().

Methods

This interface has no unique methods; inherits methods from its parent Event.

Events

unhandledrejection

Fired when a JavaScript Promise is rejected but there is no rejection handler to deal with the rejection.

rejectionhandled

Fired when a JavaScript Promise is rejected, and after the rejection is handled by the promise's rejection handling code.

Examples

window.onunhandledrejection = function(e) {
  console.log(e.reason);
}

Specifications

Browser compatibility

[1] Firefox implements the PromiseRejectionEvent interface if you go to about:config and set the dom.promise_rejection_events.enabled pref to true. However, Firefox doesn't yet actually send the unhandledrejection or understand rejectionhandled events. Completing the implementation will be addressed in bug 1362272.

See also

• Promise
• WindowEventHandlers.onrejectionhandled
• WindowEventHandlers.onunhandledrejection