来个单例模式

一、实现一个单例并不复杂，无非就是用一个变量标志当前是否已经为某个类创建过对象，如果是，下次获取该类的实例时，直接返回之前创建的对象。下面简单实现一个标准的单例模式。

var Singleton = function (name) {
    this.name = name;
    this.instance = null;
};

Singleton.prototype.getName = function(){
    console.log(this.name);
};

Singleton.getInstance = function(name) {
    //console.log(this.instance);
    if(!this.instance){ 
        this.instance = new Singleton(name);
    }
    return this.instance;
};

var a = Singleton.getInstance('aa');
var b = Singleton.getInstance('bb');
console.log(b === s); //true

<b>二、如果引进代理模式，单例模式的代码指责就更情清晰了。</b>

 var CreateDiv = function (html) {
    this.html = html;
    this.init();
};

CreateDiv.prototype.init = function() {
    var div = document.createElement('div');
    div.innerHTML = this.html;
    document.body.appendChild(div);
};

var ProxySingletonCreateDiv = (function(){
    var instance;
    return function(html) {
        if(!instance){
            instance = new CreateDiv(html);
        }
        return instance;
    }
})();

var a= new ProxySingletonCreateDiv('aa');
var b = new ProxySingletonCreateDiv('bb');