LazyMan

实现 lazyMan 按照以下方式调用

1. lazyMan("Hank")

打印："Hi, This is Hank"

2. lazyMan("Hank").sleep(10).eat('lunch')

1. 打印："Hi, This is Hank"
2. 睡了10秒后
3. 打印："Wake up after 10"
4. 打印："eat lunch"

3. lazyMan("Hank").eat("lunch").eat('dinner')

1. 打印："Hi, This is Hank"
2. 打印："eat lunch"
3. 打印："eat dinner"

4. lazyMan("Hank").sleepFirst(5).eat('lunch')

1. 睡了5秒后
2. 打印："Wake up after 5"
3. 打印："Hi, This is Hank"
4. 打印："eat lunch"

1. 实现第一个调用

function lazyMan(name){
    console.log(`Hi, This is ${name}`)
}

2. 实现第二个调用

function lazyMan(name){
    console.log(`Hi, This is ${name}`)
    const api = {
        sleep(second){
            const now = new Date()
            while(new Date() - now < (second * 1000)){}
            console.log(`Wake up after ${second}`)
            return api
        },
        eat(type){
            console.log(`eat ${type}`)
            return api
        }
    }
}

至此前三个需求都可以满足，但是到了第四个的时候，你之前写的代码得全部推翻了

3. 最终版

使用队列，先进先出

function lazyMan(name) {
  const queue = []
  const next = () => {
    const currentTask = queue.shift()
    currentTask && currentTask()
  }
  const sayHi = () => {
    console.log(`Hi,This ${name}`)
    next()
  }
  queue.push(sayHi)
  const api = {
    sleep(second) {
      const task = () => {
        setTimeout(() => {
          console.log(`Wake up after ${second}`)
          next()
        }, second * 1000)
      }
      queue.push(task)
      return api
    },
    eat(type) {
      const task = () => {
        console.log(`eat ${type}`)
        next()
      }
      queue.push(task)
      return api
    },
    sleepFirst(second) {
      const task = () => {
        setTimeout(() => {
          console.log(`Wake up after ${second}`)
          next()
        }, second * 1000)
      }
      queue.unshift(task)
      return api
    }
  }
  setTimeout(() => next(), 0)
  return api
}