CODEWITHSUNDEEP
javascriptinheritanceoverridingprototype
basilikum
basilikum

Reputation: 10528

Overriding inherited prototype method and calling the original one inside the new one

In the following piece of code, how can I access the A.prototype.log inside of B.prototype.log?

function A() {}

A.prototype.log = function () {
    console.log("A");
};

function B() {}

B.prototype = Object.create(A.prototype);
B.prototype.constructor = B;

B.prototype.log = function () {
    //call A.prototype.log here
    console.log("B");
};

var b = new B();
b.log();

I know I could just write A.prototype.log.call(this) but I thought maybe there is a more elegant way, that lets me call it in a relative way, like "call the method 'log' of the next higher instance in the prototype chain". Is something like this possible?

Upvotes: 6

Views: 2843

Answers (1)

Moritz Roessler
Moritz Roessler

Reputation: 8611

You could use Object.getPrototypeOf 

...
B.prototype.log = function () {
    Object.getPrototypeOf (B.prototype).log.call(this)
    console.log("B");
};
...
b.log(); //A B

Note: Object.getPrototypeOf is ECMASript 5, see the compatibility

There is also the non standard and deprecated __proto__ property (compatibility) which

references the same object as its internal [[Prototype]]

and would allow you to call your As' log method like this

B.prototype.__proto__.log.call(this)

But

the preferred method is to use Object.getPrototypeOf.

Upvotes: 6

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