symmetricDifference.js

symmetricDifference.js
// Symmetric Difference 
// Create a function that takes two or more arrays and returns an array of the symmetric difference (△ or ⊕) of the provided arrays.

// Given two sets (for example set A = {1, 2, 3} and set B = {2, 3, 4}), the mathematical term "symmetric difference" of two sets is the set of elements which are in either of the two sets, but not in both (A △ B = C = {1, 4}). For every additional symmetric difference you take (say on a set D = {2, 3}), you should get the set with elements which are in either of the two the sets but not both (C △ D = {1, 4} △ {2, 3} = {1, 2, 3, 4}).



function arrayDifference(arr1, arr2) {
  var difference = [];
  arr1.forEach(item => {
    if(arr2.indexOf(item) === -1) {
      difference.push(item);
    }
  });
    
  arr2.forEach(item => {
    if(arr1.indexOf(item) === -1) {
      difference.push(item);
    }
  });
  return difference;
}

function removeArrayDupes(arr) {
  var noDupes = [];
  arr.forEach( item => {
    if(noDupes.indexOf(item) === -1) {
      noDupes.push(item);
    }
  });
  return noDupes;
}


function sym(...args) {
  var arr = [];
  return args.reduce( (prev, curr) => {
    prev = arrayDifference(prev, curr);
    return removeArrayDupes(prev).sort();
  });
}

//sym([1, 2, 3], [5, 2, 1, 4]); //[3, 4, 5];

//sym([1, 2, 5], [2, 3, 5], [3, 4, 5])
//sym([3, 3, 3, 2, 5], [2, 1, 5, 7], [3, 4, 6, 6], [1, 2, 3]) 

// sym([1, 2, 3], [5, 2, 1, 4]) //should return [3, 4, 5].
// sym([1, 2, 3], [5, 2, 1, 4]) //should contain only three elements.
// sym([1, 2, 5], [2, 3, 5], [3, 4, 5]) //should return [1, 4, 5]
// sym([1, 2, 5], [2, 3, 5], [3, 4, 5]) //should contain only three elements.
// sym([1, 1, 2, 5], [2, 2, 3, 5], [3, 4, 5, 5]) //should return [1, 4, 5].
// sym([1, 1, 2, 5], [2, 2, 3, 5], [3, 4, 5, 5]) //should contain only three elements.
// sym([3, 3, 3, 2, 5], [2, 1, 5, 7], [3, 4, 6, 6], [1, 2, 3]) //should return [2, 3, 4, 6, 7].
// sym([3, 3, 3, 2, 5], [2, 1, 5, 7], [3, 4, 6, 6], [1, 2, 3]) //should contain only five elements.
//sym([3, 3, 3, 2, 5], [2, 1, 5, 7], [3, 4, 6, 6], [1, 2, 3], [5, 3, 9, 8], [1]) //should return [1, 2, 4, 5, 6, 7, 8, 9].
// sym([3, 3, 3, 2, 5], [2, 1, 5, 7], [3, 4, 6, 6], [1, 2, 3], [5, 3, 9, 8], [1]) //should contain only eight elements.