Is there a way to use map() on an array in reverse order with javascript?

Question

I want to use the map() function on a javascript array, but I would like it to operate in reverse order.

The reason is, I\'m rendering stacked React co

Answer 1

If you don't want to reverse the original array, you can make a shallow copy of it then map of the reversed array,

myArray.slice(0).reverse().map(function(...

Answer 2

Not mutating the array at all, here is a one-liner O(n) solution I came up with:

myArray.map((val, index, array) => array[array.length - 1 - index]);

Answer 3

With Named callback function

const items = [1, 2, 3]; 
const reversedItems = items.map(function iterateItems(item) {
  return item; // or any logic you want to perform
}).reverse();

Shorthand (without named callback function) - Arrow Syntax, ES6

const items = [1, 2, 3];
const reversedItems = items.map(item => item).reverse();

Here is the result

Answer 4

function mapRevers(reverse) {
    let reversed = reverse.map( (num,index,reverse) => reverse[(reverse.length-1)-index] );
    return reversed;
}

console.log(mapRevers(myArray));

I You pass the array to map Revers and in the function you return the reversed array. In the map cb you simply take the values with the index counting from 10 (length) down to 1 from the passed array

Answer 5

Another solution could be:

const reverseArray = (arr) => arr.map((_, idx, arr) => arr[arr.length - 1 - idx ]);

You basically work with the array indexes

Answer 6

You can use Array.prototype.reduceRight()

var myArray = ["a", "b", "c", "d", "e"];
var res = myArray.reduceRight(function (arr, last, index, coll) {
    console.log(last, index);
    return (arr = arr.concat(last))
}, []);
console.log(res, myArray)