In the Basic Code Solution section, near the bottom, there is a mistake.
// Check the number again, must be outside the function to about returning an object instead of undefined."
The problem is with the word “about”, it just does not seem to belong there, and, renders the sentence
unintelligible.
A better choice might be:
“Check the number outside of the function to return an object instead of undefined.”
That is my guess as to what it might mean though.