题目：

要求1：按以下要求输出
human('Jack').eat().sleep(5).go().rest(10);
// I am Jack
// Eat
// 等 5 秒
// Sleep 1s
// Go
// 等 10 秒
// Rest 10s

要求2：eat/sleep/go/rest可以改变任意顺序
human('Jack').sleep(5).eat().rest(10).go();

解答：

function human(name){
  return new Human(name)
}
function Human(name){
  this.name = name
  this.sayHello()
  this.queue = Promise.resolve()
}
Human.prototype.sayHello = function(){
  console.log(`I am ${this.name}`)
}
Human.prototype.eat = function(){
  this.queue = this.queue.then(()=>{
    return new Promise((resolve)=>{
      console.log('Eat')
      resolve()
    })
  })
  return this
}
Human.prototype.sleep = function(time){
  this.queue = this.queue.then(()=>{
    return new Promise((resolve)=>{
      setTimeout(()=>{
        console.log(`Sleep ${time}s`)
        resolve()
      },time*1000)
    })
  })
  return this
}
Human.prototype.go = function(){
  this.queue = this.queue.then(()=>{
    return new Promise((resolve)=>{
      console.log('Go')
      resolve()
    })
  })
  return this
}
Human.prototype.rest = function(time){
  this.queue = this.queue.then(()=>{
    return new Promise((resolve)=>{
      setTimeout(()=>{
        console.log(`Rest ${time}s`);
        resolve()
      },time*1000)
    })
  })
  return this
}

human('Jack').eat().sleep(5).go().rest(10);