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。
这是典型的JavaScript流程控制，问题的关键是如何实现任务的顺序执行。在Express有一个类似的东西叫中间件，这个中间件和我们这里的吃饭、睡觉等任务很类似，每一个中间件执行完成后会调用next()函数，这个函数用来调用下一个中间件。

对于这个问题，我们也可以利用相似的思路来解决，首先创建一个任务队列，然后利用next()函数来控制任务的顺序执行：

function _LazyMan(name) {    this.tasks = [];       var self = this;    var fn =(function(n){        var name = n;        return function(){            console.log("Hi! This is " + name + "!");            self.next();        }    })(name);    this.tasks.push(fn);    setTimeout(function(){        self.next();    }, 0); // 在下一个事件循环启动任务}/* 事件调度函数 */_LazyMan.prototype.next = function() {     var fn = this.tasks.shift();    fn && fn();}_LazyMan.prototype.eat = function(name) {    var self = this;    var fn =(function(name){        return function(){            console.log("Eat " + name + "~");            self.next()        }    })(name);    this.tasks.push(fn);    return this; // 实现链式调用}_LazyMan.prototype.sleep = function(time) {    var self = this;    var fn = (function(time){        return function() {            setTimeout(function(){                console.log("Wake up after " + time + "s!");                self.next();            }, time * 1000);        }    })(time);    this.tasks.push(fn);   return this;}_LazyMan.prototype.sleepFirst = function(time) {    var self = this;    var fn = (function(time) {        return function() {            setTimeout(function() {                console.log("Wake up after " + time + "s!");                self.next();            }, time * 1000);        }    })(time);    this.tasks.unshift(fn);    return this;}/* 封装 */function LazyMan(name){    return new _LazyMan(name);}