设计模式-单例模式

pattern-singleton.js

var singleton = (function () {
    function Singleton(opts) {
        this.createdAt = opts.createdAt || new Date();
    }
    
    var _instance;
    
    var static = {
        name: 'singleton',
        getInstance: function (opts) {
            if (!_instance) {
                _instance = new Singleton(opts)
            }
            return _instance;
        }
    }
    
    return static;
})();


// first time we init this singleton
var date1 = new Date();
singleton.getInstance({createdAt: date});
console.log(singleton.getInstance().createdAt); //=> Sat Feb 07 2015 17:41:21 GMT+0800 (中国标准时间)

// next time we just return this singleton
var date2 = new Date();
singleton.getInstance({createdAt: date2});
console.log(singleton.getInstance().createdAt); //=> //=> Sat Feb 07 2015 17:41:21 GMT+0800 (中国标准时间)

    

单例比起静态实例的优点是，我们需要时才会去创建它，无需浪费内存占用