how to display an object in the console with javascript like this?

Question

I have Define a "Animal" prototype object with:

2 properties: name, age and 1 function: sound, I need to create the following objects which are extended from "Animal": Cow, Sheep, Cat (I can use any name and age), then overriding the function "sound" to represent each specific sound of each animal for example:

Cow has the sound "mooo"
Sheep has the sound "bee" sheep sound
Cat has the sound "meow"

I have to use console.log to print the following result:

Name and Age of each type of animal and the sound of each type of animal

I already composed this:

const Animal = {

  Cow: {
    name: "Peppa",
    age: 12,
    sound: function cowSound() {
      alert("Moo!");
    }
  },
  Sheep: {
    name: "Shirley",
    age: 7,
    sound: function sheepSound() {
      alert("Baa!");
    }
  },
  Cat: {
    name: "Felipe",
    age: 3,
    sound: function catSound() {
      alert("Meow!");
    }
  },
};

console.log(JSON.stringify(Animal))

But the result is this: "{"Cow":{"name":"Peppa","age":12},"Sheep":{"name":"Shirley","age":7},"Cat":{"name":"Felipe","age":8}}"

Which is pretty ugly I must admit

How can I display the way I need it with JSON Stringify and see why the sound it's not displaying here, thanks in advance

That's not how you extend a class. You're creating nested properties, not new types. You need to reread your tutorial on JavaScript inheritance. — Barmar
– Barmar, Commented Apr 23, 2022 at 6:03

Amila Senadheera · Accepted Answer · 2022-04-23 07:59:06Z

Using OLOO pattern

You can use OLOO (Object linked to other objects) pattern to achieve the inheritance using Object.create method.

const Animal = {
  init: function(name, sound) {
    this.name = name;
    this.sound = sound;
  },
  makeSound: function() {
    console.log(`${this.name} has the sound "${this.sound}"`);
  },
};

// inheritance via Object.create
const Cow = Object.create(Animal);
const Sheep = Object.create(Animal);

const Cat = Object.create(Animal);
// any other methods specific to Cat
Cat.purr = function() {
  conslo.log(`${this.name} "purrs"`);
};

const animals = [];

// initializing objects
var cow = Object.create(Cow);
cow.init("Cow", "moop");
animals.push(cow);

var sheep = Object.create(Sheep);
sheep.init("Sheep", "bee");
animals.push(sheep);

var cat = Object.create(Cat);
cat.init("Cat", "meow");
animals.push(cat);

// printing
animals.forEach((animal) => {
  animal.makeSound();
});

Using prototype chaining

Javascript does not have classes actually, it has only the functions. ES6 class syntax gets transpiled into prototype chained functions like below. @oerol has provided an answer using JS classes.

Read Inheritance and the prototype chain

function Animal(name, sound) {
  this.name = name;
  this.sound = sound;
}
Animal.prototype.makeSound = function() {
  console.log(`${this.name} has the sound "${this.sound}"`);
};

// inheritance via prototype chaining
function Cow(name, sound) {
  Animal.call(this, name, sound);
}
Cow.prototype = Object.create(Animal.prototype);

function Sheep(name, sound) {
  Animal.call(this, name, sound);
}
Sheep.prototype = Object.create(Animal.prototype);

function Cat(name, sound) {
  Animal.call(this, name, sound);
}
Cat.prototype = Object.create(Animal.prototype);
Cat.prototype.purr = function() {
  conslo.log(`${this.name} "purrs"`);
};

// initializing new objects
const animals = []

var cow = new Cow("Cow", "mooo");
animals.push(cow)

var sheep = new Sheep("Sheep", "bee");
animals.push(sheep)

var cat = new Sheep("Cat", "meow");
animals.push(cat)

// printing
animals.forEach((animal) => {
  animal.makeSound();
});

mplungjan · Accepted Answer · 2022-04-23 06:29:15Z

0

You can do console.log(Animal) if you want it to be more readable. However, as @Barmar pointed out, that is not the correct way to instantiate a class. A more suitable approach would be:

class Animal {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
  sound() {
    alert("Make Sound");
  }
}

class Cow extends Animal {
  sound() {
    alert("Moo!");
  }
}

class Sheep extends Animal {
  sound() {
    alert("Meh!");
  }
}

class Cat extends Animal {
  sound() {
    alert("Miau!");
  }
}

let cow = new Cow("Peppa", 12) // Create a new object

cow.sound() // "Moo!"
console.log(cow) // Cow { name: 'Peppa', age: 12 }

edited Apr 23, 2022 at 6:29

mplungjan

180k29 gold badges183 silver badges246 bronze badges

answered Apr 23, 2022 at 6:25

oerol

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how to display an object in the console with javascript like this?

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Using OLOO pattern

Using prototype chaining

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Using OLOO pattern

Using prototype chaining

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