Finding the symmetric difference between 2 arrays

symmetric_difference.js

function sym () {
  var args_array = Array.prototype.slice.call(arguments);
  var sym_difference;
  // function that will select elements that are
  // either in array A or array B
  // Note that the symmetric difference between 3 sets includes any element present in all 3

  function symDiff (array1, array2) {
    // This will hold elements unique to either array
    var result = [];
    array1.forEach(function (elem) {
      if (array2.indexOf(elem) < 0 && result.indexOf(elem) < 0) {
        result.push(elem);
      }
    });

    array2.forEach(function (elem) {
      if (array1.indexOf(elem) < 0 && result.indexOf(elem) < 0) {
        result.push(elem);
      }
    });

    return result;
  }

  sym_difference = args_array.reduce(symDiff);
  return sym_difference;

}