findSum.js

function findSum(list, sum) {
  let listCopy = list.slice(0).sort()
  let start = 0
  let end = list.length - 1
  while(start <= end ) {
    if(list[start] + list[end] == sum) {
      return true
    }
    else if(list[start] + list[end] > sum) {
      start += 1
    }
    else if(list[start] + list[end] < sum) {
      end -= 1
    }
  }
  return false
}