Monotonic Array LeetCode solution in JavaScript

1
var isMonotonic = function (nums) {
2
  let increasingCount = 0;
3
  let decreasingCount = 0;
4
  for (let i = 1; i < nums.length; i++) {
5
    if (nums[i] > nums[i - 1]) {
6
      increasingCount++;
7
    } else if (nums[i] < nums[i - 1]) {
8
      decreasingCount++;
9
    }
10
  }
11

12
  return !(increasingCount && decreasingCount);
13
};