How can I tell if an object is an Angular $q promise?

Question

I have a pre-existing non-Angular API library in my project. It has a .request method which returns jQuery.Deferred promises. I created a simple Angular service

Answer 1

My current solution is to use instanceof:

var AngularPromise = $q.resolve().constructor;

console.log($q.resolve() instanceof AngularPromise);  // true

This guarantees to return true iff the object is indeed an Angular Promise.

Demo: https://jsfiddle.net/DerekL/cmzp7ovj/