Using generators, you can also convert any callback code into a serial one.

Here's a demo: https://github.com/vjeux/AsyncAwait

Compare

  function main() {
    multiply(1, 2, function (res) {
      multiply(res, 3, function (res) {
        multiply(res, 4, function (res) {
          console.log(res);
        })
      })
    })
  }
  main() // 24

to

  var main = async(function () {
    var [res] = yield await(multiply)(1, 2);
    [res] = yield await(multiply)(res, 3);
    [res] = yield await(multiply)(res, 4);
    console.log(res);
  });
  main() // 24