function diff(arr1, arr2) {
var newArr = arr1.concat(arr2);
var finArr = [];
for (i=0; i<newArr.length; i++){
if (arr1.indexOf(newArr[i]) === -1 || arr2.indexOf(newArr[i]) === -1) {
finArr.push(newArr[i])
}
} // Same, same; but different.
return finArr
}