main.js

function reverseArray(array) {
    empty = [];
    for(let rev of array) {
       empty.unshift(rev);
    }
    return empty;
}

function reverseArrayInPlace(array){
    for (i = 0; i < Math.floor(array.length / 2); i++){
    // loops the array from 0 to the half of the array (rounded to lower number), increases i by one each time.
        var old = array[i];
        //temporarely stores the current value of the array at the position i in the variable old.
        array[i] = array[array.length - 1 - i];
        //sets the value of the i position to the value of the last element of the array minus the current i.
        array[array.length - 1 - i] = old;
        //sets the value of the last element of the array minus the current i to the previous value (stored in the old variable).
    }
}

console.log(reverseArray(["A", "B", "C"]));
// → ["C", "B", "A"];
let arrayValue = [1, 2, 3, 4, 5];
reverseArrayInPlace(arrayValue);
console.log(arrayValue);
// → [5, 4, 3, 2, 1]