Reverse an array fast by "folding" it and counting until the middle.

quickReverse.js

// This son of a bitch goes until the middle of the array 
// and flips each item with it's mirrored item from the end
let arr = [1, 7, 2, 5, 9];
const halfLength = arr.length / 2;
const maxI = arr.length - 1;

for (let i = 0; i <= parseInt(halfLength); i=i+1) {
  let m = maxI - i;
  let a = arr[i];
  let b = arr[m];
  console.log(i, m, a, b);

  arr[i] = b;
  arr[m] = a;
}

console.log(arr);

// And a more functional way so that I can sleep better in the night
const revertArray = (array = [], index = 0) => {
    if (index >= parseInt(array.length / 2)) {
        return array;
    }

    const reverseIndex = array.length - 1 - index;
    let pin = [...array];

    pin[index] = array[reverseIndex];
    pin[reverseIndex] = array[index];

    return revertArray(pin, index + 1);
}

const mirrored = revertArray(nums);
console.log(mirrored);