RegexdrillOptional group: phone extension
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. Match a number like 555-0142, optionally followed by a space, ext, a space and 1 to 4 digits.
What this exercise teaches
\d{3}-\d{4}(?: ext \d{1,4})? treats the extension as one unit that appears once or not at all.
A hint if you get stuck
Put the whole optional part in a group, then make the group optional with ?.
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