MEPX
Chapter 3 of 10All chapters
  1. 1What a regex is
  2. 2Literals and classes
  3. 3Quantifiers
  4. 4Anchors and boundaries
  5. 5Groups and alternation
  6. 6Escaping
  7. 7Lookaround
  8. 8Flags
  9. 9When regex goes wrong
  10. 10Writing readable patterns

Chapter 3 of 10

Quantifiers

How many times.

The three plus one

An asterisk means zero or more, a plus means one or more, a question mark means zero or one, and braces give an exact count or range.

  • a{2,4} matches two to four a characters.
  • Zero-or-more can match nothing at all, which is a common source of empty matches.

Greedy and lazy

Quantifiers take as much as they can, then give characters back until the rest matches. Adding a question mark makes them lazy and take as little as possible, which is why .*? is everywhere in tag matching.