isPromiseLike(obj)

Determines if an object is "Then-able". Also see isPromise(obj) which checks for a standard Promise.

var isPromiseLike = require("can-util/js/is-promise-like/is-promise-like");

var promise = new Promise(function(resolve){
  resolve();
});

console.log(isPromiseLike(promise)); // -> true
console.log(isPromiseLike("foo bar")); // -> false