Can I add a property dynamically in javascript?

Question

Is it possible to add properties to an object at runtime? Everything seems to be in order, but are there any issues I should be aware of?

I use a third-party javascript API that has an object class that I created and added my own property after creating the instance, for example, the code below:

For example, can I do this:

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; 

Answer 1

Yes, this is called an increase in the object. This is a key feature of JavaScript.

Answer 2

In fact, you have two ways to do this in JavaScript:

• add method or property to instance (this vehicle only)

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

• add a method or property to a prototype car (all cars, even 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" ); 

Reference:

• Object.prototype

Answer 3

Yes

There is nothing wrong.

See the “Object Extension” section here: http://www.crockford.com/javascript/inheritance.html