MEPX
Chapter 2 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 2 of 10

Literals and classes

Matching characters.

Character classes

Square brackets match any one character from a set. Ranges work inside them, and a leading caret negates the whole set.

  • [aeiou] is one vowel, [0-9] is one digit, [^0-9] is one non-digit.
  • Shorthands: \d digit, \w word character, \s whitespace, and their capitals negate.

The dot

A dot matches any character except a newline by default. It is the most overused piece of syntax, and replacing it with a narrower class usually makes a pattern both faster and clearer.