【javascript设计模式】4.单例模式

<script type="text/javascript">
  var mySingleton = (function () {
    //实例保持了singleton 的一个引用
    var instance;
    function init() {
      //singleton
      //私有方法和变量
      function privateMethod() {
        console.log("I am private");
      }
      var privateVariable = "I am also private";
      var privateRandomNumber = Math.random();
      return {
        //公有方法和变量
        publicMethod: function () {
          console.log("The public can see me!");
        },
        publicProperty: "I am also public",
        getRandomNumber: function() {
          return privateRandomNumber;
        }
      };
    };
    return {
      //获取singleton 的实例，如果存在就返回，不存在就创建新实例
      getInstance: function() {
        if(!instance) {
          instance = init();
        }
        return instance;
      }
    };
  })();
  var singleA = mySingleton.getInstance();
  var singleB = mySingleton.getInstance();
  console.log(singleA.getRandomNumber()===singleB.getRandomNumber());//true
</script>

<script type="text/javascript">
  var SingletonTester = (function() {
    //options: 包含singleton所需配置信息的对象
    //var options = {name:"test",pointX:5};
    function Singleton(options) {
      //如果未提供options,则设置为空对象
      options = options || {};
      //为singleton设置一些属性
      this.name = "SingletonTester";
      this.pointX = options.pointX || 6;
      this.pointY = options.pointY || 10;
    }
    //实例持有者
    var instance;
    //静态变量和方法的模拟
    var _static = {
      name: "SingletonTester",
      //获取实例的方法，返回singleton对象的singleton实例
      getInstance: function(options) {
        if(instance === undefined) {
          instance = new Singleton(options);
        }
        return instance;
      };
      return _static;
    }
  })();
  var singletonTest = SingletonTester.getInstance({
    pointX: 5
  });
  console.log(singletonTest.pointX);//5
</script>