The following example uses the '::' operator which has a proposal already and a champion on the committee. Other than the bind operator, the example I give uses no new syntax (other than what is new to ES6), and could fairly easily be polyfilled - though I expect it could be optimized if implemented natively. If you haven't seen Clojure protocols, they allow for single dispatch polymorpism based on type, without the methods being defined as part of that type. In clojure, they use the first parameter, but for my proposal, it uses the receiver (this), and uses the bind operator to make the call look similar to a normal method call. While I haven't actually written an implementation of the Protocol class I demonstrate here, I've thought enough about it that I feel it could be done in a few different ways without too much complexity.