Regular Expressions: Character Sets

• In a character set, characters and ranges can be mixed in any order. This regex is equivalent to /[g]|[c-e]|[a]/.

• >

  /[gc-ea]/.test('a');

  Result:

  true

• >

  /[gc-ea]/.test('b');

  Result:

  false

• >

  /[gc-ea]/.test('c');

  Result:

  true

• >

  /[gc-ea]/.test('d');

  Result:

  true

• >

  /[gc-ea]/.test('h');

  Result:

  false

• We can also negate the whole character set, even if it's complex.

• >

  /[^gc-ea]/.test('a');

  Result:

  false

• >

  /[^gc-ea]/.test('d');

  Result:

  false

• >

  /[^gc-ea]/.test('b');

  Result:

  true

• If a character set ever gives you trouble, you can always break it up. For example, /[hbd-fa]/ can be thought of as /(h|b|[d-f]|a)/. This trick works for anything in regexes. Most regex features are syntactic sugar for simple features like |.

• Special characters aren't special inside a character set. For example, "." means a literal "." and "$" is a literal "$".

• >

  /[a$]/.test('$');

  Result:

  true

• >

  /[a$]/.test('a');

  Result:

  true

• >

  /[a$]/.test('^');

  Result:

  false

• >

  /^[a$]$/.test('ab');

  Result:

  false

• The ^ is only special if it's the first character in the set. There, it means "negate this set". But a ^ anywhere else in the set is just another literal character.

• >

  /[^b]/.test('b');

  Result:

  false

• >

  /[b^]/.test('b');

  Result:

  true

• >

  /[b^]/.test('^');

  Result:

  true

• >

  /[^^]/.test('b');

  Result:

  true

• >

  /[^^]/.test('^');

  Result:

  false