RegexdrillUS phone number formats
A regex exercise from Regexdrill. Solve it with a pattern box with live highlighting in your browser, checked against hidden test strings, and it is checked the moment you submit.
The task
The whole line must match. Accept (555) 123-4567, or ten digits split 3, 3 and 4 by the same separator throughout: a hyphen, a dot, or nothing.
What this exercise teaches
\(\d{3}\) \d{3}-\d{4}|\d{3}([-.]?)\d{3}\1\d{4} handles the parentheses form, and the backreference forces the same separator twice.
A hint if you get stuck
For the separated forms, capture the first separator (which may be empty) and reuse it with a backreference.
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