CodeSignal - First Reverse Try

firstReverseTry.js

/*

Reversing an array can be a tough task, especially for a novice programmer. Mary just started coding, so she would like to start with something basic at first. Instead of reversing the array entirely, she wants to swap just its first and last elements.

Given an array arr, swap its first and last elements and return the resulting array.

Example

For arr = [1, 2, 3, 4, 5], the output should be
firstReverseTry(arr) = [5, 2, 3, 4, 1].

*/

function firstReverseTry(arr) {
    // Splice first element
    let first = arr.splice(0, 1);
    // Splice last element
    let last = arr.splice(arr.length - 1, 1);

    // Push first element onto end of array
    arr.push(first);
    // Unshift last element onto beginning of array
    arr.unshift(last);

    // Splice caused the array to contain the first and last element as sub arrays, use flat to flatted the array to a single array
    return arr.flat();
}