I stopped reading after this:

  let modifiedArr = arr.map(element => element * 10);
  console.log(modifiedArr);
  Cool right :)

...

  let modifiedAarr = arr.filter((element, index) => element%2 == 0)
  Hope you got it. And don’t forgot to notice, only the first parameter is mandatory. Other two parameters are optional.
  Array Reduce