Map operator js

[alastrenok]

let cars = ['Mersedes', 'Reno', 'BMW', 'Porsche']
let up = cars.map(car =>{
      return car.toUpperCase()
})
console.log(up)

can someone explain, how is parametr ‘car’ is connected to array ‘cars’? how this return can effect the array?

[JeremyLT]

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[Catalactics]

Hey @alastrenok ,

The .map takes your callback and passes in the values inside the cars. This is what a .map function would look like:

Array.prototype.map = function(callback) {
  for (let i = 0; i < this.length; i++) {
    callback(this[i])// 'this' is the array.
  }
}

So essentially, the map function takes your function and run it by giving it the variable.

Here’s a more detailed and easier to understand explanation from an MDN article:
https://developer.mozilla.org/en-us/docs/Web/JavaScript/Reference/Global_Objects/Array/map