JavaScript Regular Expressions Quiz

Review

1. What does `/cat/` search for?

   Without anchors, the pattern can match the sequence as a substring.
2. Which pattern matches one ASCII digit?

   The range class contains digits 0 through 9.
3. What does `+` mean?

   The plus quantifier requires at least one occurrence.
4. Which pattern matches exactly `cat` as the whole input?

   Both anchors constrain the match to the input boundaries.
5. What is match[0] after a successful `exec()`?

   Capture groups begin at index 1.
6. Where are named captures exposed?

   Named groups are exposed through the `groups` property.
7. Why group `cat|dog` when applying `^` and `$` to both alternatives?

   `^(cat|dog)$` expresses one whole input that is either alternative.
8. Which flag lets `.` match line terminators?

   The `s` flag enables dotAll.
9. Which String method returns the first matching index?

   `search()` returns an index or -1.
10. What does `matchAll()` provide?

    It returns an iterator that yields match results.
11. What does positive lookahead do?

    Lookahead checks what follows while leaving it outside the consumed match.
12. Which flag enables Unicode-aware RegExp pattern semantics?

    `u` selects Unicode mode.
13. What does `\p{Letter}` represent in Unicode mode?

    Unicode property escapes use Unicode character properties.
14. Which flag enables Unicode sets mode?

    `v` enables Unicode sets mode and full Unicode matching.
15. Why can `/\d/g` be stateful when reused?

    Global matching can advance `lastIndex`.
16. What does the `d` flag add to a successful RegExp match?

    The `d` flag enables match indices, exposed through the match result's `indices` property.