JS 实现函数链式调用

let index = 0
  let stack = []
  function next(){
    let fn = stack[index]
    index++
    if(typeof fn === 'function') {
      fn()
    }
  }
  function T(name) {
    stack.push(function() {
      console.log('Hi! This is' + name)
      next()
    })
  }
  function task(name) {
    return new T(name)
  }
  T.prototype.sleep = function(delay) {
    stack.push(function() {
      setTimeout(() => {
        console.log('sleep have run end')
        next()
      },delay)
    })
    return this
  }
  T.prototype.eat = function() {
    stack.push(function() {
      console.log('eat have run end')
      next()
    })
    return this
  }
  
 task('zhangsan').sleep(1000).eat().sleep(1000).eat()
 next()