function diff(arr1, arr2) {
  var newArr = [];

  newArr = arr1.diff(arr2).concat(arr2.diff(arr1));
  
  return newArr;
}

Array.prototype.diff = function(a) {
    return this.filter(function(i) {return a.indexOf(i) < 0;});
};

function isSame(val1, val2) {
   return val1 === val2; 
}

diff([1, "calf", 3, "piglet"], [1, "calf", 3, 4] );

Compare two arrays and return a new array with any items only found in one of the original arrays.
ex.,
[1, "calf", 3, "piglet"], [1, "calf", 3, 4] should return ["piglet", 4].

Compare two arrays and return a new array with any items only found in one of the original arrays.

JavaScript