usable-promises.js

// from the brilliant mind of sb
var _catch = Promise.prototype.catch;
Promise.prototype.catch = function () {
  return _catch.call(this, function (err) { setTimeout(function () { throw(err); }, 0); });
}

okay. i get it then. so the setTimeout helps to unswallow subsequent errors in the chain, because when you setTimeout, it's async, so it gets popped back onto the call stack again after it gets queued, going through the event loop, and back onto the call stack with an intact stack trace.