Changing an Object's Type in JavaScript

Question

I have an array of existing object defined with JSON. The objects are obviously of the Object type. How do I associate them with a custom object type to give them specific functionality?

Answer 1

The way that'll work in all browsers is to either augment each item in the array with the properties and methods you want, or pass the object to a constructor and create a new object based on the old object's properties and methods.

Or if you don't care about IE:

var obj = {
    name : "Jeremy"
};

function CustomType() {
    this.name = this.name || "someValue";
    this.greeting = "Hi";
}

CustomType.prototype.sayHi = function() {
    alert(this.greeting + ", " + this.name);
};

obj.__proto__ = CustomType.prototype;
obj.constructor.call(obj);

obj.sayHi();