Generators 2

completion record

function* gen() {
  try {
    yield 1
    yield 3
  } finally {
    yield 4
  }
}

// 4

iterator closing

for (let smth of someGen()) {
  if (...)
    break // итератор должен закрыться и вызваться метод return
}

function* gen() {
  yield* [1, 2, 3]
}
[...gen()] // [1, 2, 3]

function* gen2() {
  yield [1, 2, 3]
}
[...gen2()] // [[1, 2, 3]]

Async/await (stage3)

let all = (...args) => Promise.all(args)

async () => {
  let [aR, bR, cR] = await all(a,b,c)
}

spec link