bonfire-diff-two-arrays.js

// Bonfire: Diff Two Arrays
// Author: @minsooshin
// Challenge: http://www.freecodecamp.com/challenges/bonfire-diff-two-arrays
// Learn to Code at Free Code Camp (www.freecodecamp.com)

function diff(arr1, arr2) {
  var newArr = [];
  
  function check(a1, a2) {
    var obj = {};
    a1.map(function(val) {
      obj[val] = true;
    });

    a2.map(function(val) {
      if (!obj[val]) newArr.push(val);
    });
  }
  
  check(arr1, arr2);
  check(arr2, arr1);

  // Same, same; but different.
  return newArr;
}

diff(["andesite", "grass", "dirt", "pink wool", "dead shrub"], ["diorite", "andesite", "grass", "dirt", "dead shrub"]);