YYYY-MM-DD format
Match a date in YYYY-MM-DD format. Check the shape only: 4 ASCII digits, hyphen, 2 digits, hyphen, 2 digits. Do not validate the calendar; 2024-99-99 matches.
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Write a regular expression
Match the required strings and reject the others. Practice regular expressions with concrete examples.
- Character classes
- Anchors
- Matches and exclusions
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Numbers only
Match an entire non-empty string containing only ASCII digits 0–9. No sign, whitespace or decimal separator.
Preview challenge → Free account required to solveSimplified email address
Match the entire simplified address: a non-empty local part using ASCII letters, digits and ._%+-, then a domain with alphanumeric labels (hyphens only inside), at least…
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How should you approach these challenges?
Regular expression exercises teach you to recognise text formats and reject non-matching data. They are useful for filtering logs, searching text and checking the shape of form values. Matching a format does not always prove validity, such as whether a calendar date exists.
Compare strings that should match with those that must be rejected. Build a clear pattern expressing the difference first. Check start and end anchors, repetition counts and escaped characters. After each change, run every example, not just the last failing case.
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