Question

For a JavaScript project we want to introduce object inheritance to decrease code duplication. However, I cannot quite get it working the way I want and need some help.

We use the module pattern. Suppose there is a super element:

a.namespace('a.elements.Element');
a.elements.Element = (function() {
    // public API -- constructor
    Element = function(properties) {
        this.id = properties.id;
    };

    // public API -- prototype
    Element.prototype = {
        getID: function() {
            return this.id;
        }
    };

    return Element;
}());

And an element inheriting from this super element:

a.namespace('a.elements.SubElement');
a.elements.SubElement = (function() {
    // public API -- constructor
    SubElement = function(properties) {
        // inheritance happens here
        // ???
        this.color = properties.color;
        this.bogus = this.id + 1;
    };

    // public API -- prototype
    SubElement.prototype = {
        getColor: function() {
            return this.color;
        }
    };

    return SubElement;
}());

You will notice that I’m not quite sure how to implement the inheritance itself. In the constructor I have to be able to pass the parameter to the super object constructor and create a super element that is then used to create the inherited one. I need a (comfortable) possibility to access the properties of the super object within the constructor of the new object. Ideally I could operate on the super object as if it was part of the new object.

I also want to be able to create a new SubElement and call getID() on it.

What I want to accomplish seems like the traditional class based inheritance. However, I’d like to do it using prototypal inheritance since that’s the JavaScript way. Is that even doable?

Thanks in advance!

EDIT: Fixed usage of private variables as suggested in the comments.
EDIT2: Another change of the code: It’s important that id is accessible from the constructor of SubElement.

Answer 1

You can do class-like inheritance using JavaScript’s prototypical inheritance if you like. See this other answer for a full example and discussion, which you can easily fit into your pattern.