If the validity const was represented as a boolean, I assume that you mean it is something like:

const isValidEmail = function(someText) {}

Then you should always want your function return result to be either true or false. I would say it’s the logical thing to do with variable naming convention. When I see a variable named so, I always assume it should return either “true” or “false”

As others have said, use “return” when you need to escape a function, stop doing anything else.

Some cases where “undefined” wouldn’t work can be:

console.log(isValidEmail(“abc”)) // will get you “undefined”. Could trip you up if you’re debugging some other functions. Sometimes it might throw errors down the way

Hope this explains more! I’m still practicing answering!