js单例模式的两种方案

复制代码 代码如下:

//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);

复制代码 代码如下:

//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