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PromiseRejectionEvent.reason

The read-only PromiseRejection property reason read-only property is any JavaScript value or Object which provides the reason passed into Promise.reject(). This in theory provides information about why the promise was rejected.

Syntax

reason = PromiseRejectionEvent.reason

Value

A value or object which provides information you can use to understand why the promise was rejected. This could be anything from an error code to an object with text, links, and whatever else you might wish to include.

Examples

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

Specifications

Specification Status Comment
HTML Living Standard
The definition of 'PromiseRejectionEvent.reason' in that specification.
Living Standard Initial definition.

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
Basic support 49 ? No
Disabled
No
Disabled
Firefox doesn't yet send the unhandledrejection or understand rejectionhandled events. Completing the implementation will be addressed in bug 1362272.
Disabled This feature is behind the dom.promise_rejection_events.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.
No No No
Mobile
Android webview Chrome for Android Edge Mobile Firefox for Android Opera for Android iOS Safari Samsung Internet
Basic support ? No ? No
Disabled
No
Disabled
Firefox doesn't yet send the unhandledrejection or understand rejectionhandled events. Completing the implementation will be addressed in bug 1362272.
Disabled This feature is behind the dom.promise_rejection_events.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.
No No ?

See also

© 2005–2018 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/PromiseRejectionEvent/reason