Regex Hunter
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Character classes

Master character classes: build sets of allowed characters, sweep whole ranges, flip a set inside-out with negation, and lean on the shorthands every hunter knows by heart.

Read the rules: Character classes in the Guide →Drill it: Character castles →

Builds on Hunter basics

What you'll learn

Character sets Ranges Negation Shorthands Hex ranges

Steps · 13

  1. 01One slot, many choicesBriefing
  2. 02Character setsHunt
  3. 03Ranges: a-zHunt
  4. 04Ranges: 0-9Hunt
  5. 05Negated setsHunt
  6. 06Shorthand: \dHunt
  7. 07The shorthand trioExample
  8. 08Negated shorthandsHunt
  9. 09Metacharacters go literalHunt
  10. 10Combined rangesHunt
  11. 11Uppercase rangeHunt
  12. 12Golf: shortest catchHunt
  13. 13Slots masteredBriefing

Regex character classes, ranges and shorthands

A character class lets one slot in a pattern accept a choice of characters. Write the options inside square brackets and the class matches any single one of them. gr[ae]y accepts both spellings of the colour, because the slot after gr may be an a or an e. Classes are how you say "a vowel here" or "some digit there" without writing out every possible word.

Classes get more useful with ranges and negation. A hyphen between two characters covers everything in between, so [1-5] is any digit from one to five and [A-Za-z] is any plain letter. A caret right after the opening bracket flips the set: [^,] is any character except a comma. Whatever is inside, a class always uses up exactly one character.

Some sets come up so often that regex gives them shorthands. \d is a digit, \w is a word character (letter, digit or underscore) and \s is whitespace. Their capital forms \D, \W and \S mean the opposite. Reach for a class whenever a hunt says "any of these" or "anything but these" for a single position.

Examples

  1. /gr[ae]y/

    Catches

    • gray
    • grey
    • greyhound

    Spares

    • groan
    • grid

    The class offers two choices for the third letter and nothing else.

  2. /[1-5]star/

    Catches

    • 1star
    • 5stars
    • my3star

    Spares

    • 6star
    • 0star
    • star

    A range covers every digit from 1 to 5 in one slot.

  3. /z[^z]/

    Catches

    • zap
    • lazy
    • ozone

    Spares

    • buzz
    • fizz
    • quiz

    A negated class still needs a character, so a z at the very end doesn't match, and neither does a z followed by another z.

  4. /\d\s\d/

    Catches

    • 1 2
    • room 4 5

    Spares

    • 12
    • 1-2

    Shorthands combine like letters: a digit, a space, then another digit.

Common mistakes

  • Reading a class as a word. [cat] matches one c, a or t, not the word cat, so it also catches tea and act.
  • Writing ranges that cross cases. [a-Z] is an error in JavaScript, and [A-z] quietly lets in symbols such as [, ^ and _; use [A-Za-z].
  • Expecting \w to cover accented letters. In JavaScript it means only ASCII letters, digits and underscore, so the é in café counts as a non-word character.

Read the rules: Character classes in the Guide →Drill it: Character castles →

Read more: Regex character classes: \d, \w, \s, [a-z] and their traps →