的Javascript：最好Singleton模式

Question

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Simplest/Cleanest way to implement singleton in JavaScript?

我用这个模式来单身，本例中的单是地球脉动：

var NAMESPACE = function() { 

    var privateFunction1 = function() { 
     privateFunction2(); 
    }; 

    var privateFunction2 = function() { 
     alert('I\'m private!'); 
    }; 

    var Constructors = {}; 

    Constructors.PlanetEarth = function() { 
     privateFunction1(); 
     privateFunction2(); 
    }; 

    Constructors.PlanetEarth.prototype = { 
     someMethod: function() { 
      if (console && console.log) { 
       console.log('some method');    
      } 
     } 
    }; 

    Constructors.Person = function (name, address) { 
     this.name = name; 
     this.address = address; 
    }; 

    Constructors.Person.prototype = { 
     walk: function() { 
      alert('STOMP!'); 
     } 
    }; 

    return { 
     Person: Constructors.Person, // there can be many 
     PlanetEarth: new Constructors.PlanetEarth() // there can only be one! 
    }; 

}(); 

由于地球脉动的构造保持私密，也只能是一个。

现在，有人告诉我，这种自制的东西并不是最好的，主要是因为我没有学历教育，而且我倾向于用愚蠢的方式解决问题。你会提出什么样的更好替代我的方法，其中更好被定义为风格上更好和/或更强大？

Answer 1

为什么要为单个对象使用构造函数和原型？

以上等同于：

var earth= { 
    someMethod: function() { 
     if (console && console.log) 
      console.log('some method');        
    } 
}; 
privateFunction1(); 
privateFunction2(); 

return { 
    Person: Constructors.Person, 
    PlanetEarth: earth 
}; 

Answer 2

找到最好的解决办法： http://code.google.com/p/jslibs/wiki/JavascriptTips#Singleton_pattern

function MySingletonClass() { 

    if (arguments.callee._singletonInstance) { 
    return arguments.callee._singletonInstance; 
    } 

    arguments.callee._singletonInstance = this; 

    this.Foo = function() { 
    // ... 
    }; 
} 

var a = new MySingletonClass(); 
var b = MySingletonClass(); 
console.log(a === b); // prints: true 

对于那些谁想要严格的版本：

(function (global) { 
    "use strict"; 
    var MySingletonClass = function() { 

    if (MySingletonClass.prototype._singletonInstance) { 
     return MySingletonClass.prototype._singletonInstance; 
    } 

    MySingletonClass.prototype._singletonInstance = this; 

    this.Foo = function() { 
     // ... 
    }; 
    }; 

var a = new MySingletonClass(); 
var b = MySingletonClass(); 
global.result = a === b; 

} (window)); 

console.log(result); 

Answer 3

Extending上述职位由汤姆，如果你需要一个类型声明并使用变量访问单例实例，下面的代码可能会有所帮助。我喜欢这种表示法，因为代码很少有自我指导。

function SingletonClass(){ 
    if (arguments.callee.instance) 
     return arguments.callee.instance; 
    arguments.callee.instance = this; 
} 


SingletonClass.getInstance = function() { 
    var singletonClass = new SingletonClass(); 
    return singletonClass; 
}; 

要访问的单身，你会

var singleTon = SingletonClass.getInstance(); 

Answer 4

function SingletonClass() 
{ 
    // demo variable 
    var names = []; 

    // instance of the singleton 
    this.singletonInstance = null; 

    // Get the instance of the SingletonClass 
    // If there is no instance in this.singletonInstance, instanciate one 
    var getInstance = function() { 
     if (!this.singletonInstance) { 
      // create a instance 
      this.singletonInstance = createInstance(); 
     } 

     // return the instance of the singletonClass 
     return this.singletonInstance; 
    } 

    // function for the creation of the SingletonClass class 
    var createInstance = function() { 

     // public methodes 
     return { 
      add : function(name) { 
       names.push(name); 
      }, 
      names : function() { 
       return names; 
      } 
     } 
    } 

    // wen constructed the getInstance is automaticly called and return the SingletonClass instance 
    return getInstance(); 
} 

var obj1 = new SingletonClass(); 
obj1.add("Jim"); 
console.log(obj1.names()); 
// prints: ["Jim"] 

var obj2 = new SingletonClass(); 
obj2.add("Ralph"); 
console.log(obj1.names()); 
// Ralph is added to the singleton instance and there for also acceseble by obj1 
// prints: ["Jim", "Ralph"] 
console.log(obj2.names()); 
// prints: ["Jim", "Ralph"] 

obj1.add("Bart"); 
console.log(obj2.names()); 
// prints: ["Jim", "Ralph", "Bart"]