🤔 For what prototype??

what is prototype?

simply put, special property in object

For example

function Worker(name, age) {
  this.name = name
  this.age = age
}

// ⭐ prototype !!
Worker.prototype.msg = function() {
  console.log('I am ' + this.name)
}

const maria = new Worker('Maria', 20)
const kaziu = new Worker('Kaziu', 27)
const jhon = new Worker('Jhon', 37)

maria.msg() // I am Maria
kaziu.msg() // I am Kaziu
jhon.msg() // I am Jhon 

▼ But we could write like that

function Worker(name, age) {
  this.name = name
  this.age = age
  // ⭐ like this ####################
  this.msg = function() {
    console.log('I am ' + this.name)
  }
  // ###########################
}

const maria = new Worker('Maria', 20)
const kaziu = new Worker('Kaziu', 27)
const jhon = new Worker('Jhon', 37)

maria.msg() // I am Maria
kaziu.msg() // I am Kaziu
jhon.msg() // I am Jhon

🤔 So for what we use prototype ??
😎 One of the reason is memory management

If you don't use prototype, each instance would create new function on new memory preference when each time instance is created

Otherwise function doesn't create each time when instance is created as you see in image.
Each instance just look for preference of prototype (= instances look for memory place of prototype function)

ref. from this course