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map() Array Method

map() is a method used on arrays to handle iteration. It uses a callback function on every Element in the array it’s called on. It’s one of my most used array methods and quite possibly my favorite.

The great thing about map(), is that it creates a new array instead of mutating the original.

If you don’t know already, mutation…nay nay, you don’t want that.

Immutability increases predictability and predictable code is good as far as I’m concerned.

Let’s touch on the syntax by creating a brief example so you can familiarize yourself with map().

const numbersArray = [18, 35, 62]

const squaredNumbers = numbersArray.map(number => number * number)

console.log(squaredNumbers)

This is as simple as it gets, but I’ll break it down and have more practical examples as we move along.

Looking back at the code block now. numbersArray is created to hold our three numbers in an array.

We store Within the map method, we setup a callback function using the array function syntax. number is used as the argument and simply refers to every item in the numbersArray.

When we call the map method, it needs an identifier for every item in the array it’s called on. You can name


Written by@David Quick
Hi ✌️ I'm Dave, a developer from NY. I write web development articles for all. This is my journal to you. Enjoy!