"Simple First Draft": addWeirdStuffRefactor.js

const addWeirdStuffRefactor = (arrayOne, arrayTwo) => {
  const sumOfEvensInArrayTwo = arrayTwo.reduce(
    (sumOfEvens, itemTwo) =>
      itemTwo % 2 === 0 ? sumOfEvens + itemTwo : sumOfEvens,
    0 // Start with an initial value of 0
  )
  const sumOfOddsInArrayTwo = arrayTwo.reduce(
    (sumOfOdds, itemTwo) =>
      itemTwo % 2 === 1 ? sumOfOdds + itemTwo : sumOfOdds,
    0 // Start with an initial value of 0
  )

  const outputArray = []
  for (const itemOne of arrayOne) {
    // Add sum of odds if itemOne is less than 10; add sum of evens if >= 10
    let outputValue =
      itemOne < 10
        ? itemOne + sumOfOddsInArrayTwo
        : itemOne + sumOfEvensInArrayTwo
    // Add one to each itemOne if arrayTwo contains an element greater than 20
    outputValue += arrayTwo.some((itemTwo) => itemTwo > 20) ? 1 : 0
    outputArray.push(outputValue)
  }
  return outputArray
}

console.log("------------")
console.log(
  `[${addWeirdStuffRefactor(
    [1, 3, 5, 17, 15],
    [1, 2, 3, 4, 5]
  )}] should equal [10,12,14,23,21]`
)
console.log(
  `[${addWeirdStuffRefactor(
    [1, 3, 5, 17, 15, 1],
    [1, 2, 3, 4, 5, 22]
  )}] should equal [11,13,15,46,44,11]`
)