一、實現(xiàn)一個單例并不復雜，無非就是用一個變量標志當前是否已經(jīng)為某個類創(chuàng)建過對象，如果是，下次獲取該類的實例時，直接返回之前創(chuàng)建的對象。下面簡單實現(xiàn)一個標準的單例模式。

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、如果引進代理模式，單例模式的代碼指責就更情清晰了。</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');