ECMAScript doesn&#x27;t have cancellable promises, but then again it doesn&#x27;t have observables or async iterators either.<p>Native observables are less capable in this regard than native promises since they&#x27;re non existent yet.<p>Bluebird promises are cancellable.<p>For what it&#x27;s worth I&#x27;ve discussed this personally with Meijer (it&#x27;s Meijer, not Meijers) and he agrees that cancellable promises are not problematic one bit.<p>Promises, observables and other async primitives all co-exist just fine :)