Array Filtering (also modify the original array)

modify.js

function modify(arr) {
  let i = 0
  while (i < arr.length) {
    if (isNaN(arr[i])) {
      arr.splice(i, 1)
      --i
    } else {
      i++
    }
  }
  return arr
}

var arrr = [1, 2, 'b', 'h', 3, 4, 12]
modify(arrr)
console.log(arrr)