Slidding window pattern

maxSubArraySum.js

function maxSubarraySum(arr, num) {
  let maxSum = 0;
  let tempSum = 0;
  if (arr.length < num) { return null }
  for (let i = 0; i < num; i++) {
    maxSum += arr[i]
  }
  tempSum = maxSum;
  for (let i = num; i < arr.length; i++) {
        tempSum = tempSum - arrp[i - num] + arr[i];
    amxSum = Math.max(maxSum, tempSum)
  }
  return maxSUM;
}