Is it possible to get a boolean return value when using set.add() in JavaScript?

I am using a loop to add to a Set in JavaScript. Something like:

let mySet = new Set();

$('li').each(function() {
  mySet.add($(this).text());
})

This works fine. However, I wanted to see if I could leverage .add() to tell me if the item was successfully added or not, without iterating through the set looking for a match again.

Does anyone know if this is possible?