// 使用 Promise 简单封装 setTimeout
const wait = ms => new Promise(resolve => setTimeout(resolve, ms))

;(async () => {
  // 同步
  function debounce(delay, action, init = undefined) {
    let flag
    let result = init
    return function(...args) {
      if (flag) clearTimeout(flag)
      flag = setTimeout(() => {
        const temp = action.apply(this, args)
        if (temp instanceof Promise) {
          temp.then(res => (result = res))
        } else {
          result = temp
        }
      }, delay)
      return result
    }
  }

  const get = async i => i

  console.log(await get(1))
  console.log(await get(2))
  // 注意，修改默认值为 Promise
  const fn = debounce(10, get, 0)
  console.log(fn(3)) // 0
  console.log(fn(4)) // 0
  await wait(20)
  console.log(fn(5)) // 4
})()
;(async () => {
  // 异步
  const debounce = (delay, action, init = undefined) => {
    let flag
    let result = init
    return new Proxy(action, {
      apply(target, thisArg, args) {
        return new Promise(resolve => {
          if (flag) clearTimeout(flag)
          flag = setTimeout(() => {
            result = Reflect.apply(target, thisArg, args)
            resolve(result)
          }, delay)
          setTimeout(() => {
            resolve(result)
          }, delay)
        })
      },
    })
  }

  const get = async i => i

  console.log(await get(1))
  console.log(await get(2))
  // 注意，修改默认值为 Promise
  const fn = debounce(10, get, 0)
  fn(3).then(i => console.log(i)) // 0
  fn(4).then(i => console.log(i)) // 4
  await wait(20)
  fn(5).then(i => console.log(i)) // 5
})()