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Stop using Array.map() everywhere πŸ₯΅

Stop using Array.map() everywhere πŸ₯΅

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Suprabha Supi
Β·Dec 29, 2021Β·

2 min read

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Most of the time I used to see the snippet like this πŸ‘‡

const fruits = ["apple", "orange", "cherry"];
let text = "";
document.getElementById("main").innerHTML = text;
fruits.map(i => text += i );

In the above snippet, we are adding fruits text to the DOM in main ID. It seems there is no issue in the above snippet, Though there is one major issue, which we will be going see today.

Let's understand the issue by definition of map, map() method creates a new array populated with the results of calling a provided function on every element in the calling array.

example:

let n = [1, 2, 3, 4];
let add = n.map(i => i + 2);
console.log(add); // [3, 4, 5, 6]

NOTE: Using map() method means returning a new collection of an array.

As discussed, map() method always returns a new array, so if you don’t have any use of a new array then never use map() method. When you just need to iterate through an array, I will always recommend using other array methods like forEach or for..of.

example:

const fruits = ["apple", "orange", "cherry"];
let text = "";
fruits.forEach(myFunction);

document.getElementById("main").innerHTML = text;

function myFunction(item, index) {
  text += index + ": " + item + "<br>"; 
}

Why should we care about it? πŸ™„

As we know, map() method always returns an array. If you just need to update DOM then storing those elements into memory form doesn't add any point. Of course, for a small chunk of numbers nothing is going to happen, however, if we take a larger number here then it affects the performance side as it will store the value in memory which will be redundant.

Summary β…€

Stop using map() method, if you just need to iterate through an array. Start using forEach or for...of method, if you want to iterate through an array.

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