You are given an array of integers nums. Return the length of the longest subarray of nums which is either strictly increasing or strictly decreasing.

longestMonotonicSubarray.js

/**
 * @param {number[]} nums
 * @return {number}
 */
var longestMonotonicSubarray = function(nums) {
     if (nums.length === 0) return 0;

    let maxLength = 1;
    let currentLength = 1;
    let increasing = null;

    for (let i = 1; i < nums.length; i++) {
        if (nums[i] > nums[i - 1]) {
            // If the subarray is strictly increasing
            if (increasing !== true) {
                increasing = true;
                currentLength = 2; // Reset current length for new subarray
            } else {
                currentLength++;
            }
        } else if (nums[i] < nums[i - 1]) {
            // If the subarray is strictly decreasing
            if (increasing !== false) {
                increasing = false;
                currentLength = 2; // Reset current length for new subarray
            } else {
                currentLength++;
            }
        } else {
            // Reset when the elements are equal
            increasing = null;
            currentLength = 1;
        }
        maxLength = Math.max(maxLength, currentLength);
    }

    return maxLength;
};