CODEWITHSUNDEEP
javascriptoopsuper
Toffee Conmigo
Toffee Conmigo

Reputation: 87

"super" keyword cannot access parent property in javascript

class Base{
    constructor(val){
        this.val = val;
    }
    basep = 'default1';
    basef(){
        return 2;
    }
}

class Test1 extends Base{
    constructor(val,name){
        super(val);
        this.name=name;
         
    }
    getp(){
        console.log(this.name,this.val);
        console.log(this.basep); //(in case of proerty) result: 'default1'.  if "this" is changed to "super" ===>  result: undefined
        console.log(super.basef()); //(in case of methods) this and super both work.
    }
}

test= new Test1(1,3);
test.getp();

In java 'this' and 'super' worked both fine to get parents property but it seems in javascript only this works. why is the difference?

Upvotes: 1

Views: 565

Answers (1)

Bergi
Bergi

Reputation: 664385

In Java, attribute names are put in a scope, and you can have two different attributes with the same name if they were created by different classes. This is not how it works in JavaScript with prototypical inheritance at all, though.

In JavaScript, data properties (that are created by assignment) are owned by the object itself. The parent constructor created the .basep property directly on the child instance. this.hasOwnProperty('basep') will be true.

The super keyword is used to access properties on the parent's .prototype object, regardless of what the current this value is, but still allows calling them on the this object. The basef method lives as a property on Base.prototype, basep does not.

Upvotes: 2

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