Array_Element_Parity.js

/*In this Kata, you will be given an array of integers whose elements have both a negative and a positive value, except for one integer that is either only negative or only positive. Your task will be to find that integer.

Examples:

[1, -1, 2, -2, 3] => 3

3 has no matching negative appearance

[-3, 1, 2, 3, -1, -4, -2] => -4

-4 has no matching positive appearance

[1, -1, 2, -2, 3, 3] => 3

(the only-positive or only-negative integer may appear more than once)*/


function solve(arr){
  arr = [...new Set(arr)]
  return arr.reduce((a,b)=> a + b)
  
}