Find the odd int (6kyu) [JavaScript]

Chek kata on Codewars

Description:

Given an array of integers, find the one that appears an odd number of times.

There will always be only one integer that appears an odd number of times.

HashTable

function findOdd(arr) {
  var hashTable = {};
  arr.forEach(function(el){
    hashTable[el] ? hashTable[el]++ : hashTable[el] = 1;
  });

  for(let prop in hashTable) {2
    if(hashTable[prop] % 2 !== 0) return Number(prop);
  }
}

Find + Filter

function findOdd(arr) {
  return arr.find((item) => arr.filter(el => el == item).length % 2)
}

XOR

function findOdd(arr) {
  return arr.reduce((a, b) => a ^ b)
}