if not in set

Hi there… pretty new to this as in started today ?

im trying an if statement, but the user is entering one of a specifc set of characters into a prompt variable… i am then trying to write an if statement that says “if it doesnt equal one of these”, or “if its not in this set” do this… is there any way of doing this without doing loads of else if statements for each one?

Cheers for any help

Also in #JavaScript _↴