Regex Tests

Let's work on some regex. Using this set of numbers 123-939-7878 complete the following levels.

• You can use PHP, Python or JavaScript for this challenge.
• Create one answer per level.

Level 1 - The simplest way

Yes, this is a trick question. What is the simplest way to check for EXACTLY this set of numbers? Remember the simplest way is not always the correct way ;)

Level 2 - Character classes

Use character classes to check for the numbers. You can also use sets if you want

Level 3 - Short hand only

Now simplify the answer using short hand syntax. You can also use sets if you want

Level 4 - Group those numbers

Let's turn those numbers into groups.

Level 5 - You see hyphens I see brackets

What happens if the hyphens are sometimes open and closed brackets like this:

(123)(939)(7878)

Or like this

(123)-939-(7878)

Adjust your answer to cope with hyphens and/or brackets.