Peter Mols Peter Mols - 15 days ago 5
Javascript Question

Catch all unhandled javascript promise rejections

I would like to catch all unhandled exceptions/rejections that take place within a javascript Promise. Is there a good method for catching them without adding a

.catch(..)
on each end of the Promise chain? (in case of forgetting to add this, the error silently disappears).

The developer console in Google Chrome can log them, I like to log them as well in a production environment.

For normal javascript exceptions I use the
window.onerror
function, but the errors from a Promise call this function.

Example:

window.onerror = function (e) {
alert("unhandled error: " + e);
};

var p = new Promise(function (resolve, reject) {
var nullObject = null;
// Raise a TypeError: Cannot read property 'forceNullError' of null
var x = nullObject.forceNullError();
resolve();
});

p.then(function () { alert('success'); });


JSFiddle: https://jsfiddle.net/f7zwej6L/

*) I noticed that WinJS has a
.done(..)
method for what I want, but Native Promises don't.

Answer

The whole world is waiting for the unhandledrejection and rejectionhandled events. As of March 2016, Chrome is now the first to support it.

Example:

window.addEventListener('unhandledrejection', function(event) {
    console.error('Unhandled rejection (promise: ', event.promise, ', reason: ', event.reason, ').');
});

Specification: HTML Living Standard

Mozilla Developer: onrejectionhandled, onunhandledrejection

Chromium Issues: 495801, 393913