WorkerGlobalScope: rejectionhandled event

Note: This feature is only available in Web Workers.

The rejectionhandled event is sent to the script's global scope (typically WorkerGlobalScope) whenever a rejected Promise is handled late, i.e., when a handler is attached to the promise after its rejection had caused an unhandledrejection event.

This can be used in debugging and for general application resiliency, in tandem with the unhandledrejection event, which is sent when a promise is rejected but there is no handler for the rejection at the time.

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

js
self.addEventListener("rejectionhandled", (event) => {});
self.onrejectionhandled = (event) => {};

Event type

Event properties

PromiseRejectionEvent.promise Read only

The Promise that was rejected.

PromiseRejectionEvent.reason Read only

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

Example

You can use the rejectionhandled event to log promises that get rejected to the console, along with the reasons why they were rejected:

js
self.addEventListener("rejectionhandled", (event) => {
  console.log(`Promise rejected; reason: ${event.reason}`);
});

Specifications

Specification
HTML
# handler-workerglobalscope-onrejectionhandled

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
rejectionhandled event

Legend

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Full support
Full support

See also