The PromiseRejectionEvent interface represents events which are sent to the global script context when JavaScript Promises are rejected. These events are particularly useful for telemetry and debugging purposes.

For details, see Promise rejection events.

PromiseRejectionEvent()

Creates a PromiseRejectionEvent event, given the type of event (unhandledrejection or rejectionhandled) and other details.

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().

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

rejectionhandled

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

unhandledrejection

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

This simple example catches unhandled promise rejections and logs them for debugging purposes.

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

• Using promises
• Promise
• rejectionhandled
• unhandledrejection