考察知识点：闭包，事件轮询机制，链式调用，队列
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。下面是 ES6 的实现方式，如果用 ES5 来写要在维护 this 方面多写一些代码
class _LazyMan {
constructor(name) {
this.tasks = [];
const task = () => {
console.log(`Hi! This is ${name}`);
this.next();
}
this.tasks.push(task);
setTimeout(() => { // 把 this.next() 放到调用栈清空之后执行
this.next();
}, 0);
}
next() {
const task = this.tasks.shift(); // 取第一个任务执行
task && task();
}
sleep(time) {
this._sleepWrapper(time, false);
return this; // 链式调用
}
sleepFirst(time) {
this._sleepWrapper(time, true);
return this;
}
_sleepWrapper(time, first) {
const task = () => {
setTimeout(() => {
console.log(`Wake up after ${time}`);
this.next();
}, time * 1000)
}
if (first) {
this.tasks.unshift(task); // 放到任务队列顶部
} else {
this.tasks.push(task); // 放到任务队列尾部
}
}
eat(name) {
const task = () => {
console.log(`Eat ${name}`);
this.next();
}
this.tasks.push(task);
return this;
}
}
function LazyMan(name) {
return new _LazyMan(name);
}下面是 ES5 的实现方式
<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge"/>
<title>lazyMan</title>
</head>
<body>
<p>请打开控制台进行输入代码、调试</p>
<script type="text/javascript">
(function(window, undefined){
var taskList = [];
// 类
function LazyMan(){};
LazyMan.prototype.eat = function(str){
subscribe("eat", str);
return this;
};
LazyMan.prototype.sleep = function(num){
subscribe("sleep", num);
return this;
};
LazyMan.prototype.sleepFirst = function(num){
subscribe("sleepFirst", num);
return this;
};
// 订阅
function subscribe(){
var param = {},
args = Array.prototype.slice.call(arguments);
if(args.length < 1){
throw new Error("subscribe 参数不能为空!");
}
param.msg = args[0];
param.args = args.slice(1); // 函数的参数列表
if(param.msg == "sleepFirst"){
taskList.unshift(param);
}else{
taskList.push(param);
}
}
// 发布
function publish(){
if(taskList.length > 0){
run(taskList.shift());
}
}
// 鸭子叫
function run(option){
var msg = option.msg,
args = option.args;
switch(msg){
case "lazyMan": lazyMan.apply(null, args);break;
case "eat": eat.apply(null, args);break;
case "sleep": sleep.apply(null,args);break;
case "sleepFirst": sleepFirst.apply(null,args);break;
default:;
}
}
// 具体方法
function lazyMan(str){
lazyManLog("Hi!This is "+ str +"!");
publish();
}
function eat(str){
lazyManLog("Eat "+ str +"~");
publish();
}
function sleep(num){
setTimeout(function(){
lazyManLog("Wake up after "+ num);
publish();
}, num*1000);
}
function sleepFirst(num){
setTimeout(function(){
lazyManLog("Wake up after "+ num);
publish();
}, num*1000);
}
// 输出文字
function lazyManLog(str){
console.log(str);
}
// 暴露接口
window.LazyMan = function(str){
subscribe("lazyMan", str);
setTimeout(function(){
publish();
}, 0);
return new LazyMan();
};
})(window);
</script>
</body>
</html>