Question

I was playing around with javascript prototype chain inheritance and i came accross this funny behaviour.

I have a parent class and a child class

//class parent
function parent(param_1) {
    this.param_1 = param_1;

    this.getObjWithParam = function(val) {
        console.log(this);
        console.log("Constructor value in parent class " + this.param_1);
        console.log("tguha ----> parent,  val " + val);
    };
};

//class child
function child(param_1) {
    parent.call(this, [ param_1 ]);
};

var childObj = new child(100);
childObj.getObjWithParam(200);

and i get the output as

**>child**
Constructor value in parent class 100
tguha ----> parent,  val 200

and nowhere i’m doing //child.prototype = new parent();
and still the parent class is inherited.

Could anyone help me by explaining this scenario please.

Answer 1

The word prototype does not appear in this code. So nothing is being inherited. You create a new child and then explicitly run the parent constructor function on that new child. The parent constructor function then add a method to to the new child.

If you put getObjWithParam on parent.prototype.getObjWithParam instead then you will see that it will not carry over.