Solving the 'Card details interactive form' challenge

What are you most proud of, and what would you do differently next time?

In this challenge I trained my JavaScript a lot and overcame some challenges. Next time I will try to make the code smaller and simpler.

What challenges did you encounter, and how did you overcome them?

In this project I encountered some challenges, such as ensuring that when typing the card number there was a space for every 4 numbers entered. And also when you type a letter in the number field, an error message appears.