单例模式

//方案一
var SingletonTester = (function () {
//单例方法
function Singleton(args) {
var args = args || {};
this.name = 'SingletonTester'; //方法对外的属性，另外一种方式就是返回对象
this.pointX = args.pointX || 6;
this.pointY = args.pointY || 10;
}

    //单例实例 
    var instance; 

    //返回对象 
    return { 
        name: 'SingletonTester', 

        getInstance: function (args) { 
            if (instance === undefined) { 
                instance = new Singleton(args); 
            } 
            return instance; 
        } 
    }; 
})(); //直接执行该方法 

//测试 
var test = SingletonTester.getInstance({ pointX: 5 }); 
console.log(test.pointX); 

//方案二
function Universe() {
// 判断是否存在实例
if (typeof Universe.instance === 'object') {
return Universe.instance;
}

  // 其它内容 
  this.start_time = 0; 
  this.bang = "Big"; 

  // 缓存 
  Universe.instance = this; 

  // 隐式返回this 

}

// 测试
var uni = new Universe();
var uni2 = new Universe();
console.log(uni === uni2); // true