- Email-ish:
^[^\s@]+@[^\s@]+\.[^\s@]+$ - UUID v4:
^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$ - ISO date:
^\d{4}-\d{2}-\d{2}$ - Trim whitespace (JS):
str.replace(/^\s+|\s+$/g, "")
Tip: always add tests—regexes lie to confident minds.