Using call() method vs setting prototype property for inheritance

Question

I'm a somewhat beginner, I used to know the very basics but stopped programming after that.

In JavaScript's Prototypal Inheritance, I've found/learned two ways of doing this.

Using the prototype property of a constructor:

function Mammal(name) {
    this.name = name,
    this.order = "Mammal",

    this.sayHi = function() {
        console.log("My name is " + this.name);
    }
}

function Cat(name) {
    this.name = name;
    this.family = "Felidae";
}

Cat.prototype = new Mammal();

let lion = new Cat("Lion");

Or by calling the Mammal.call(this, name) method.

What are the differences between the two results? Which one is to be preferred if they're different?

Neither one is to be preferred; a combination of the two is closer to the correct version, which is Cat.prototype = Object.create(Mammal.prototype);, Mammal.call(this, name); in Cat, and putting sayHi on Mammal.prototype. Better, use a class, which does all this and also improves other behaviours. class Cat extends Mammal {} — Ry-
– Ry- ♦, Commented Nov 14, 2021 at 12:48

nima · Accepted Answer · 2021-11-15 09:41:12Z

0

Usually, we use class keyword to define a class in many program languages. In Javascript you can define your classes using simple and clear syntax using class keyword.

Either you can use the two ways you mentioned, you can use class keyword:

class Mammal {
  constructor(name) {
    this.name = name;
    this.order = 'Mammal';
  }

  sayHi() {
    console.log('My name is ' + this.name);
  }
}

class Cat extends Mammal {
  constructor(props) {
    super(props);
    this.family = 'Felidae';
  }
}

let lion = new Cat('Lion');

lion.sayHi();

3 Comments

Abhinav Jha Over a year ago

If the class keyword is just synctactical sugar, which method is it using under the hood, call() or property ?

nima Over a year ago

@Kaiser "syntactical sugar" is not correct properly at all, there are many sources you can read about this misleading keyword: medium.com/@naveenkarippai/… and webreflection.medium.com/… also read javascript.info/class and stackoverflow.com/questions/36419713/…

Abhinav Jha Over a year ago

I appreciate your help. Thanks!

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