Question

我一直在研究对象文字等。我正在创建一个具有我的播放器的各种属性的游戏。这些prorpeties存储在多个组中，例如他的船和它的所有属性，他的wepaon以及它的所有属性等。结果我将这些属性存储到对象文字中。

我不希望我的对象值被覆盖。我在这里遇到了一篇文章http://www.gabordemooij.com/jsoop.html，并且好奇这样的事情是否会让对象值容易被覆盖，这是一个健康的开始......

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

我在jsFiddle设置了一个小测试，以演示揭示对象模式是一件多么美妙的事情：

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

失败是因为声音是局部变量，无法在对象之外引用。

如果你想引用它，你需要制作一个吸气剂。

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"));

保护对象文字并防止被覆盖的良好实践

2 个答案: