avgVanilla.js

const example = [1,2,5,7,9,11,13,17,19]
const example2 = [-2,5,8,14,1,5,-9,-10,2]

// imperative programming
avg = function(arr) {
  let sum = 0
  // iterate through array
  for (let i = 0; i < arr.length; i++) {
    // add each number to var sum
    sum += (arr[i])
  }
  let length = arr.length
  return sum/length
}

console.log(avg(example))  // 9.333
console.log(avg(example2)) // 1.555