Catch all unhandled javascript promise rejections

javascript es6-promise
Peter Mols picture Peter Mols · Jul 17, 2015 · Viewed 24.6k times · Source

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

Valentin Shergin picture Valentin Shergin · Oct 5, 2015

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

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