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

Here is my TypeScript solution that is both O(n) and more efficient than the other solutions by preventing a run through the array twice:

function reverseMap<T, O>(arg: T[], fn: (a: T) => O) {
   return arg.map((_, i, arr) => fn(arr[arr.length - i - 1]))
}

In JavaScript:

const reverseMap = (arg, fn) => arg.map((_, i, arr) => fn(arr[arr.length - 1 - i]))

// Or 

function reverseMap(arg, fn) {
    return arg.map((_, i, arr) => fn(arr[arr.length - i - 1]))
}

Answer 2

An old question but for new viewers, this is the best way to reverse array using map

var myArray = ['a', 'b', 'c', 'd', 'e'];
[...myArray].map(() => myArray.pop());

Answer 3

I prefer to write the mapReverse function once, then use it. Also this doesn't need to copy the array.

function mapReverse(array, fn) {
    return array.reduceRight(function (result, el) {
        result.push(fn(el));
        return result;
    }, []);
}

console.log(mapReverse([1, 2, 3], function (i) { return i; }))
// [ 3, 2, 1 ]
console.log(mapReverse([1, 2, 3], function (i) { return i * 2; }))
// [ 6, 4, 2 ]

Answer 4

You can do myArray.reverse() first.

var myArray = ['a', 'b', 'c', 'd', 'e'];
myArray.reverse().map(function (el, index, coll) {
    console.log(el + " ")
});