Why does this if statement not recognise numbers?

Question

This code works fine on letters, returning if the letters are upper or lower case but it always returns the number as "6 is a uppercaseletter"

let userLetter = prompt("Please enter an uppercase, lowercase letter or a number");


if (typeof userLetter === 'number') {
    userLetter = userNumber;
    alert(`${userNumber} is a number`);
} else if (userLetter.toUpperCase() === userLetter) {
    alert(`${userLetter} is a uppercase letter`);
} else if (userLetter.toLowerCase() === userLetter) {
    alert(`${userLetter} is a lowercase letter`);
} else {
    alert('Something went wrong');
}
 

I expected the typeof operator would recognise that the input is a number but it doesn't. When a number is entered it always returns the uppercase option.

Answer 1

prompt always returns a string (for which typeof returns "string").

You could use isNaN instead.

if (!isNaN(userLetter)) alert(`${userLetter} is a number`);