create map filter from scratch

gistfile1.txt

function mapArray(arr,cb){
  let res = [];
  for(const e of arr){
    res.push(cb(e));
  }
  return res;
}

function filterArray(arr, cb){
  let res = [];
  for(const e of arr){
    const isAllowed = cb(e);
    if(isAllowed){
      res.push(e)
    }
  }
  return res;
}