Regex for three letters and four numbers?

Question

I have this regex I am supposed to create that accepts the following formats:

1. Any 3 letters (case-insensitive, no other characters except for alphabetic characters)
2. Any 2 letters with a dash in between (case-insensitive)
3. Any 4 digits

This is what I have come up with so far: ^([a-zA-Z]([a-zA-Z]|-)[a-zA-Z])|[0-9]{4}$

The issue with this regex is that it accepts a combination of 4 letters as well, but I only want three consecutive letters. What do I need to change in my regex to accomplish this?

Answer 1

You may use:

^(?:[a-zA-Z][a-zA-Z-][a-zA-Z]|[0-9]{4})$

RegEx Demo

RegEx Details:

• ^: Start
• (?:: Start non-capture group that match either of these 2 alternatives
  • [a-zA-Z][a-zA-Z-][a-zA-Z]: Match 3 letters or a letter-letter
  • |: OR
  • [0-9]{4}: Match 4 digits
• ): End non-capture group
• $: End