Algorithms - Find the Symmetric Difference

Tell us what’s happening:
Describe your issue in detail here.

  **Your code so far**
function sym(args) {
return args;
}

sym([1, 2, 3], [5, 2, 1, 4]);[3,4,5]
sym([1,2,3],[5,2,1,4],[3,4,5]);[1,2,3,4,5]
  **Your browser information:**

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Challenge: Algorithms - Find the Symmetric Difference

Link to the challenge:

hey there~

What kind of help do you need with this?