Proper use of Class Inheritance Javascript OOP

Question

There seems to be some problem on my syntax but I don't know what seems to be the problem.

I am using prototyping inheritance (if I'm not mistaken)

The program should be like this:

• The class must inherit the features of the parent, so when I call on the function it will display some text.

Here is what my code looks like:

function myFunction() {

    var Property = function(dom,height,width){

        this.dom = document.createElement("img");
        this.height = height;
        this.width = width;

        };

    Property.prototype.display = function() {

    text("The image has: ", this.height+200, this.width+200);
    };

    Image.prototype = Object.create(Property.prototype)

    var firstImage = function(dom,height,width){
        Property.call(this, dom, height,width);
    };

    var image1 = new Image("image.jpg", 10 , 10);
    image1.display();
}

Answer 1

(I think naomik's is the better approach, but if you are trying to just figure out what's happening, see the following:)

Apparently Image does not allow extension (at least in Firefox where I am testing) because it does work with another class.

If, after this line...

Image.prototype = Object.create(Property.prototype)

...you add:

alert(Image.prototype.display)

...you will see that it is undefined, whereas if you add:

function MyImage () {}
MyImage.prototype = Object.create(Property.prototype)
alert(MyImage.prototype.display); // Alerts the "display" function

I guess that is because you cannot replace the whole prototype. Try adding to the prototype instead (though this won't help with the constructor).