reinvert_control.js

// when I have to write some node for the first time ...

Promise.fromGen = function (gen, v) {
  return new Promise(function (resolve) {
    var cont = function (g, v) {
      var x = g.next(v);
      if (x.done) { return resolve(x.value); }
      return x.value.then((v) => cont(g, v));
    };
    cont(gen(v));
  });
}

Promise.prototype.feedGen = function (gen) {
  return this.then((v) => Promise.fromGen(gen, v));
};

Promise.resolve("!").feedGen(function* (v) {
  var x = yield Promise.resolve("hello");
  var y = yield Promise.resolve("world");
  return x + ", " + y + v;
}).then(console.log);