JS中异步调用可以转化为同步调用吗？

Question

function wait() {
        const p = () => ({
            value: new Promise(resolve => setTimeout(() => resolve(), 3000))
        })
        let state = {
            next: () => {
                state.next = programPart
                return p()
            }
        }
        function programPart() {
            console.log('unlocked1')
            state.next = programPart2
            return p()
        }
        function programPart2() {
            console.log('unlocked2')
            console.log('it\'s sync!!')
            return {
                value: void 0
            }
        }
        return state
    }

这个函数该如何调用？

Answer 1

var state = wait()
state.next()
    .value
    .then(() => state.next().value)
    .then(() => state.next().value)
    .then(() => console.log(state.next()))

Answer 2

可以使用async函数来实现视觉上的同步调用。async是 Generator 函数的语法糖。

const fn = async function () {
  let state = wait();
  await state.next().value;
  await state.next().value;
  return state.next().value;
}
fn()