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 = {…

symmetric-difference.js

function sym(args) {
  //Put the arguments into an array
  var arrArgs = Array.prototype.slice.call(arguments);
  
  //Function to compare two arrays by reducing each one in
  //comparison with the other. Check if the item in first array
  //is also in the second array, if it isn't push it to the accumulator.
  //then repeat the other way around.
  function compareArrays(arr1, arr2){
    var arr1red = arr1.reduce(function(collect, current){
      //to remove doubles, check the item is not already collected.
      if(!arr2.includes(current) && !collect.includes(current)){
        collect.push(current);
      }
      return collect;
    },[]);
    
    var arr2red = arr2.reduce(function(collect, current){
      if(!arr1.includes(current) && !collect.includes(current)){
        collect.push(current);
      }
      return collect;
    },[]);
    //join the two arrays together and return the result
    return arr1red.concat(arr2red);
  }
  
  //Reduce the arguments array to a single array that contains only elements
  //that are the symmetric difference. (First compare the first two arrays, then
  //compare the result of that with the next array);
  return arrArgs.reduce(compareArrays);
    
}

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

Very nice solution

Such a very genius answer!