我可以在 javascript 中动态添加属性吗？

Can I add a property dynamically in javascript?

提问by capdragon

Is it okay to add properties to an object at runtime? It seems to run okay but are there any issues I should be aware of?

可以在运行时向对象添加属性吗？它似乎运行正常，但有什么我应该注意的问题吗？

I'm using a 3rd party javascript API which has an object class, which I've instantiated and added my own property to after instantiation, like the code below:

我正在使用 3rd 方 javascript API，它有一个对象类，我已经实例化并在实例化后添加了我自己的属性，如下面的代码：

For example can I do this:

例如，我可以这样做：

var Car = function (id, type) {
    this.id = id;
    this.type = type;
};

var myCar = new Car(1,"Nissan");

// CAN I DO THIS: (needsWork not a property of object Car)
myCar.needsWork = true;

回答by ?ime Vidas

Yea, this is called object augmentation. It is a key feature in JavaScript.

是的，这称为对象增强。它是 JavaScript 中的一个关键特性。

回答by Sean Patrick Floyd

Actually, you have two ways to do that in JavaScript:

实际上，在 JavaScript 中有两种方法可以做到这一点：

1. add a method or property to an instance (this car only)

   var myCar = new Car(1,"Nissan");
   myCar.needsWork = true;
   

2. add a method or property to the car prototype (all cars, even already existing ones)

   var myCar = new Car(1, "Nissan");
   var biggerCar = new Car(2, "Hummer");
   Car.prototype.needsWork = true;
   alert( myCar.needsWork && biggerCar.needsWork 
           ?  "We need work"
           : "Something wrong here"
   );
   

1. 向实例添加方法或属性（仅限本车）

   var myCar = new Car(1,"Nissan");
   myCar.needsWork = true;
   

2. 向汽车原型添加方法或属性（所有汽车，甚至已经存在的汽车）

   var myCar = new Car(1, "Nissan");
   var biggerCar = new Car(2, "Hummer");
   Car.prototype.needsWork = true;
   alert( myCar.needsWork && biggerCar.needsWork 
           ?  "We need work"
           : "Something wrong here"
   );
   

Reference:

参考：

• Object.prototype

• 对象.prototype

回答by Adam

Yes

是的

There is nothing wrong with that.

没有什么不妥。

See Object Augmentation here: http://www.crockford.com/javascript/inheritance.html

请参阅此处的对象增强：http: //www.crockford.com/javascript/inheritance.html