Function rotate

javascript/0189-rotate-array.js:10–17

(nums, k)

 * @return {void} Do not return anything, modify nums in-place instead.
 */
var rotate = function (nums, k) {
    // if the k exceeds the length of nums.
    k = k % nums.length;

    nums.reverse();
    reversePortionOfArray(nums, 0, k - 1);
    reversePortionOfArray(nums, k, nums.length - 1);
};

var reversePortionOfArray = function (nums, start, end) {
    while (start < end) {