Average every third element in an array for a more concise dataset

Average array elements for dataset

let arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
    avgs = [],
    sum = 0;

arr.forEach((el, i) => {
  sum += el;
  if ((i + 1) % 3 == 0) {
    avgs.push(sum / 3);
    sum = 0;
  }
});

console.log(avgs);