2021-07-15 实现一个LazyMan

非原创，面试挂了，整理一下答案

原文地址->掘金-子非-如何实现一个LazyMan
实现一个LazyMan，可以按照以下方式调用:

LazyMan(“Hank”)输出:
Hi! This is Hank!

LazyMan(“Hank”).sleep(10).eat(“dinner”)输出
Hi! This is Hank!
//等待10秒..
Wake up after 10
Eat dinner~

LazyMan(“Hank”).eat(“dinner”).eat(“supper”)输出
Hi This is Hank!
Eat dinner~
Eat supper~

LazyMan(“Hank”).sleepFirst(5).eat(“supper”)输出
//等待5秒
Wake up after 5
Hi This is Hank!
Eat supper
以此类推。

ES6 Class 实现

class _LazyMan {
  constructor(name) {
    this.tasks = [];  // tasks维护将要执行的操作
    const task = () => {
      console.log(`Hi! This is ${name}!`);
      this.next();  // 当前任务执行完毕后，继续执行下一个，后续task同理
    };
    this.tasks.push(task);
    setTimeout(()=>{
      this.next();
    }, 0);
  }
  next() {
    let task = this.tasks.shift();
    task && task();
  }
  sleepFirst(time) {  // 优先执行，需放置在队首
    this.sleep(time, true);
    return this;
  }
  sleep(time, first = false) {
    let task = () => {
      const DELAY = time * 1000;
      setTimeout(()=>{
        console.log(`Wake up after ${time}`);
        this.next();
      }, DELAY);
    };
    if(first) {
      this.tasks.unshift(task);
    } else {
      this.tasks.push(task);
    }
    return this;
  }
  eat(food) {
    let task = () => {
      console.log(`Eat ${food}~`);
      this.next();
    };
    this.tasks.push(task);
    return this;
  }
}

const LazyMan = (name) => {
  return new _LazyMan(name);
}
LazyMan('Hank').sleep(10).eat('dinner').sleepFirst(3)

原型链继承，借用箭头函数实现版

function _LazyMan(name) {
  this.tasks = [];
  let task = () => {
    console.log(`Hi! This is ${name}!`);
    this.next();
  };
  this.tasks.push(task);
  setTimeout(() => {
    this.next();
  }, 0);
  return this;
}

_LazyMan.prototype.next = function () {
  const task = this.tasks.shift();
  task && task();
};

_LazyMan.prototype.sleep = function (time, isFirst = false) {
  const DELAY = time * 1000;
  let task = () => {
    setTimeout(() => {
      console.log(`Wark up after ${time}`);
      this.next();
    }, DELAY);
  };
  isFirst ? this.tasks.unshift(task) : this.tasks.push(task);
  return this;
};

_LazyMan.prototype.sleepFirst = function (time) {
  this.sleep(time, true);
  return this;
};

_LazyMan.prototype.eat = function (food) {
  let task = () => {
    console.log(`Eat ${food}~`);
    this.next();
  };
  this.tasks.push(task);
  return this;
};

function LazyMan(name) {
  return new _LazyMan(name);
}

LazyMan('Hank').eat('dinner').sleep(3).sleepFirst(5);