保護對象文字並防止被覆蓋的良好做法

Question

我一直在對對象文字等進行一些研究。我正在製作一款遊戲，其中包含來自我的玩家的各種屬性。這些prorpeties被存儲在多個組中，比如他的船和所有的屬性，他的wepaon以及所有的屬性等。因此，我一直在將這些屬性存儲到對象文字中。

我不希望我的對象值被覆蓋。我碰到這裏的一篇文章http://www.gabordemooij.com/jsoop.html跑，和好奇，如果是這樣，這將是一個健康的開始，從容易被覆蓋保持對象的值...

Cat = { 
    createNew: function() { 
    var cat = {}; 
    var sound = "meow"; //sound is local 
    cat.makeSound= function(){ 
     //can reach sound from here 
     alert(sound); 
    } 
    return cat; 
    } 
} 

var cat = Cat.createNew(); 
cat.makeSound(); 
//but can't reach sound from here 
alert(cat.sound); //fail! 

Answer 1

我已經建立了在jsFiddle一個小的測試證明顯露的對象模式是一個多麼美妙的事情：

var Test = (function(){ 
    var priv = "Banana"; 
    var public = "Orange"; 
    var pubobj = {name:"Cheese"}; 

    function constructor(){ 
     this.public = public; 
     this.pubobj = pubobj; 

     this.instance = {name:"Grape"}; 

     this.instanceMethod = function(){ 
      return priv; 
     }; 
    }; 

    constructor.prototype.private = function(){ 
     return priv; 
    };    

    return constructor; 

})(); 

var myTest = new Test(); 

console.log(myTest.public);  //Orange 
console.log(myTest.priv);  //undefined 
console.log(myTest.private()); //Banana 

var myTest2 = new Test(); 

console.log(myTest.public === myTest2.public); //true (they are both primitives with the same value) 
console.log(myTest.private === myTest2.private); //true (the methods share the same instance) 

myTest.public = "cheese"; 
console.log(myTest.public, myTest2.public);  // "cheese", "Orange" (overwriting the primitive doesn't change the primitive of myTest2) 

myTest.pubobj.name = "Melon";     
console.log(myTest.pubobj, myTest2.pubobj);  //the name property for both is now "Melon" (both test objects share the same instance of pubobj) 

myTest.instance.name = "Raspberry"; 
console.log(myTest.instance, myTest2.instance); // the name of myTest2.instance is unchanged 

console.log(myTest.instanceMethod === myTest2.instanceMethod);​ // false (while identical, these methods have separate instances) 

Answer 2

它失敗，因爲聲音是不能被引用的局部變量對象之外。

如果你想引用它，你需要做一個getter。

Cat = { 
    createNew: function() { 
    var cat = {}; 
    var sound = "meow"; //sound is local 
    cat.getSound= function(){ 
     //can reach sound from here 
     return sound; 
    } 
    return cat; 
    } 
} 


var cat = Cat.createNew(); 
alert(cat.getSound()); 

或

Cat = { 
    createNew: function() { 
    var cat = {}; 

    var props = { 
     sound : "meow", 
     foo : "bar" 
    }; 

    cat.get= function(key){    
     return props[key]; 
    } 
    return cat; 
    } 
} 

var cat = Cat.createNew(); 
alert(cat.get("sound"));