generator function

generator.js

function asyncDouble(x) {
  var deferred = Promise.defer();
  setTimeout(function() {
    deferred.resolve(x*2);
  }, 1000);
  return deferred.promise;
}

function consumer(generator){
  var cursor = generator();
  var value;
  function loop() {
    var data = cursor.next(value);
    if (data.done) {
      return;
    } else {
      data.value.then(function(x) {
        value = x;
        loop();
      })
    }
  }
  loop();
}

function* myGen() {
  const data1 = yield asyncDouble(1);
  console.log("double1: " + data1);
  const data2 = yield asyncDouble(2);
  console.log("double2: " + data2);
  const data3 = yield asyncDouble(3);
  console.log("double3: " + data3);
}

consumer(myGen); 

// double1: 2
// double2: 4
// double3: 6