Question 198892 in Javascript Question posted in
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Javascript – How to put an array in a constructor in JS?

For instace – I need to create a class that can be used to create multiple farms. Each farm must contain an id, a location and an array of animals. Each animal must have a name and quantity (so basically an animal will be an object).
I don’t know how to put this array of animals inside the class.

class Farms {
  constructor (id, location, animals) {
  this.id = id;
  this.location = location;
  this.animals = animals;

} – how can I make ‘animals’ into an array?

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4

Answers


  1. 0

    If you want to go OOP way then it’s better to create an Animal class as well and pass an array of that.

    class Animal {
  constructor(name, qty) {
    this.name = name
    this.qty = qty
  }
}

const animal1 = new Animal('A name', 1)
const animal2 = new Animal('Another name', 2)

const farm = new Farm(1, 'location', [animal1, animal2])

    If you don’t want to create Animal class. You can just pass array of objects that defines animal.

    const farm = new Farm(1, 'location', [
  { name: 'A name', qty: 1 },
  { name: 'Another name', qty: 2 }
])
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  2. 0

    Create Animal class, instantiate some animals from that class, and pass it to Farm object:

    class Animal {
  constructor(name, quantity) {
    this.name = name;
    this.quantity = quantity;
  }
}
class Farm {
  constructor(id, location, animals) {
    this.id = id;
    this.location = location;
    this.animals = animals;
  }
}
const animals = [
  new Animal("Bird", 2),
  new Animal("Rabbit", 3),
  new Animal("Dogs", 1)
];
const farm = new Farm(1, "MyFarm", animals);
console.log(farm);

    Note: It’s generally a good practice to use singular nouns instead of plural nouns for naming classes.
    e.g. name your class Farm instead of Farms.

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  3. 0

    For the record: without the class sugar and as OOP as anything:

    const farm = Farm( 1, "MyFarm", 
  [Animal(`Pig`, 3), Animal(`Donkey`, 2), Animal()] );

document.body.insertAdjacentHTML(`beforeend`, `
  <pre>${JSON.stringify(farm, null, 2)}</pre>`);
  
function Animal(name = `unknown`, quantity = 1) {
  return { name, quantity };
}

function Farm(id, location = `unknown`, animals = []) {
  return { id, location, animals };
}
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  4. 0

    Small refactoring to @XMehdi01 answer. Keep constructor arguments followed by an underscore to keep the readability and clarity for future.

    class Animal {
  constructor(_name, _quantity) {
    this.name = _name;
    this.quantity = _quantity;
  }
}
class Farm {
  constructor(_id, _location, _animals) {
    this.id = _id;
    this.location = _location;
    this.animals = _animals;
  }
}
const animals = [
  new Animal("dog", Math.floor(Math.random() * 100000)),
  new Animal("cat", Math.floor(Math.random() * 100000)),
  new Animal("shark", Math.floor(Math.random() * 100000))
];
let FarmObject = new Farm(crypto.randomUUID(), "Las Vegas", animals);
console.log(FarmObject);
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