Diagonal Difference (HackerRank)

diagonal-difference.js

// Without reduce
function diagonalDifference(arr) {
    let sum = 0;
    for (let i = 0; i <= arr.length - 1; i++) {
        sum += arr[i][i] - arr[i].reverse()[i];
    }
    return Math.abs(sum);
}

// With reduce
function diagonalDifference(arr) { 
    return Math.abs(arr.reduce((acc, array, i) => acc += array[i] - array.reverse()[i], 0));
}

// Verify square matrix
const matrix = Array(4).fill(Array(4).fill(0));
function isSquare(elem, index, array) {
    return elem.length == array.length;
}