Window: rejectionhandled event

The rejectionhandled event is sent to the script's global scope (usually window but also Worker) whenever a JavaScript Promise is rejected but after the promise rejection has been handled.

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.

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

window.addEventListener("rejectionhandled", event => {
  console.log("Promise rejected; reason: " + event.reason);
}, false);

• Promise rejection events in Using Promises
• PromiseRejectionEvent
• Promise
• unhandledrejection