This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

The reason read-only property of the PromiseRejection returns the rejection reason for the Promise that the current notification is about. Although the reason can be undefined, it is generally an Error object, like in exception handling.


var myPromiseRejectionReason = myPromiseRejection.reason;


A DOMString that represents the promise's rejection reason.


var myPromiseRejection = new PromiseRejection();
var myPromiseRejectionReason = myPromiseRejection.reason;


Specification Status Comment
Unhandled Rejection Tracking Browser Events
The definition of 'PromiseRejectionEvent' in that specification.
Editor's Draft Initial definition.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 49.0 45.0 (45.0) No support ? No support
Feature Android Android Webview Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support No support 49.0 45.0 (45.0) (Yes) No support ? No support 49.0

See also


© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.

API Experimental Interface PromiseRejection Property reason Reference