Return Early Pattern for Functions : Better Solutions Please

I don’t know how to solve this challenge except in this way.
According to the challenge, it says; Modify the function abTest so that if a or b are less than 0 the function will immediately exit with a value of undefined.
I would love if someone can help. Thanks.

Your code so far

// Setup
function abTest(a, b) {
  // Only change code below this line
  if (a < 0 || b < 0) {
    return "undefined";
  // Only change code above this line

  return Math.round(Math.pow(Math.sqrt(a) + Math.sqrt(b), 2));

// Change values below to test your code

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Link to the challenge:

You are returning a string, instead in JavaScript undefined (without quotes) is a specific value

Thanks, I just solved it.