The rejectionhandled
event is sent to the script's global scope (usually window
but also Worker
) whenever a rejected JavaScript 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.
Use the event name in methods like addEventListener()
, or set an event handler property.
addEventListener("rejectionhandled", (event) => {});
onrejectionhandled = (event) => {};
In addition to the Window
interface, the event handler property onrejectionhandled
is also available on the following targets:
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,
);