Answer 1

不用类的实现，js里基本用类实现的用对象也可以实现。

LazyMan('Tony')
// Hi I am Tony

LazyMan('Tony')
  .sleep(10)
  .eat('lunch')
// Hi I am Tony
// 等待了10秒...
// I am eating lunch

LazyMan('Tony')
  .eat('lunch')
  .sleep(10)
  .eat('dinner')
// Hi I am Tony
// I am eating lunch
// 等待了10秒...
// I am eating diner

LazyMan('Tony')
  .eat('lunch')
  .eat('dinner')
  .sleepFirst(5)
  .sleep(10)
  .eat('junk food')
// Hi I am Tony
// 等待了5秒...
// I am eating lunch
// I am eating dinner
// 等待了10秒...
// I am eating junk food

下面是实现

let man = {
  queue: []
}

function LazyMan(name) {
  console.log(`Hi I am ${name}`)
  setTimeout(() => {
    man.next()
  }, 0)
  return man
}

man.eat = food => {
  man.queue.push(() => {
    console.log(`I am eating ${food}`)
    man.next()
  })
  return man
}

man.sleep = timeout => {
  man.queue.push(() => {
    setTimeout(() => {
      console.log(`等待了${timeout}秒`)
      man.next()
    }, timeout * 1000)
  })
  return man
}

man.sleepFirst = timeout => {
  man.queue.unshift(() => {
    setTimeout(() => {
      console.log(`等待了${timeout}秒`)
      man.next()
    }, timeout * 1000)
  })
  return man
}

man.next = () => {
  if (man.queue.length > 0) {
    man.queue.shift()()
  }
}