function* test() {
  let x = 1
  yield x + 1;
  yield x + 2;
  return x + 3;
}
const gen = test()
console.log(gen)
console.log(gen.next())
console.log(gen.next())
console.log(gen.next())
console.log(gen.next())

function asyncFn() {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      console.log(111)
      resolve(222)
    }, 1000)
  })
}
function asyncFn2() {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      console.log(333)
      resolve(444)
    }, 1000)
  })
}
function* test() {
  yield asyncFn();
  yield asyncFn2();
  yield ‘ddd‘;
  return  3;
}
const gen = test()
function step(gen) {
  const { value, done } = gen.next()
  res = value
  if(done) return
  // Promise.resolve如果参数是 Promise 实例，那么Promise.resolve将不做任何修改、原封不动地返回这个实例。
  Promise.resolve(value).then((res) => {
    step(gen)
    console.log(res)
  })
}
step(gen)