regex to match repeated consonant

Question

How can I detect with a regex expression if the same consonant is repeated three times or more?

My idea is to match words like tttoo

Answer 1

I'd personally solve this in reverse; instead of using [b-df-hj-np-tv-z], I'd go with the double-negative, [^\W_aeiou].

/([^\W_aeiou])\1\1+/i

This has a character class that uses a double negative: match anything except a non-word-character, an underscore, or a vowel. Ignoring non-ASCII vowels, only consonants can match this. Saving a match, the regex then seeks a match of that same consonant (case-insensitive), then one or more again, which brings us to 3+ consecutive consonants.