实现下面的函数:
new Test("test").firstSleep(3).sleep(5).eat("dinner")
//等待3秒
//test
//等待5秒
//dinner链式调用没什么可说的 return this 就好了 ，此处的sleep 乍一看确实会引发一些思考，关键是异步之后我的this 在哪里 ；那这个时候我就可以创建一个异步队列 ；整个实现可以分为三个核心部分
1，串接所有this （通过return this的方式）
2，把所有任务放到任务队列里面
3，通过一个 方法有序执行队列里面的任务
具体实现如下：
function Test(name){this.task = [];let fn = ()=>{console.log(name);this.next();}this.task.push(fn);setTimeout(()=>{this.next();},0)return this;}Test.prototype.firstSleep = function(timer){console.time("firstSleep")let that = this;let fn = ()=>{setTimeout(()=>{console.timeEnd("firstSleep");that.next();},timer*1000)}this.task.unshift(fn);return this;}Test.prototype.sleep = function(timer){console.time("sleep")let that = this;let fn = ()=>{setTimeout(()=>{console.timeEnd("sleep");that.next();},timer*1000)}this.task.push(fn);return this;}Test.prototype.eat = function(dinner){let that = this;let fn = ()=>{console.log(dinner);that.next();}this.task.push(fn);return this;}Test.prototype.next = function(dinner){let fn = this.task.shift();fn&&fn()}new Test("test").firstSleep(3).sleep(5).eat("dinner")