Character Classes

Function	RegExp equivalent	Explanation
word	\w	Match alphanumeric characters and underscore
not.word not(word)	\W	Match anything other than \w
digit	\d	Match a character between 0 to 9
not.digit not(digit)	\D	Match anything other than a digit
whitespace	\s	Match all types of whitespace characters
not.whitespace not(whitespace)	\S	Match anything other than a whitespace
char	.	Match any character other than newline (or including line terminators when single line flag is set) Note: not.char does not exist because it does not match anything
charIn`a-z_-` charIn('a-z', '_-') charIn`a-z` `_-`	[a-z_-]	Match a character listed in the group. A hyphen denotes a range of characters, such as a-z. †
notCharIn`a-z_-` not.charIn`a-z_-` notCharIn('a-z', '_-') notCharIn`a-z` `_-`	[^a-z_-]	Match a character not listed in the group. †
charRange`a` `z` charRange('a', 'z')	[a-z]	Match a character ranging from the first char to the second one. Escape sequences are supported and the two characters must be in order.
notCharRange`a` `z` not.charRange`a` `z` notCharRange('a', 'z')	[^a-z]	Match a character not in the range of first to second char. Escape sequences are supported and the two characters must be in order.

† Notes on character classes

charIn accepts a list of strings and special sequences, but you can also combine the list into one string if you prefer:

• charIn('a-z0-9' + whitespace)

• charIn`a-z0-9${whitespace}`

• charIn`a-z0-9\s`

However, combining a list of options into one string is not equivalent to a simple string concatenation. - is escaped at the beginning and end of each string in the list, so charIn`a-` `z` matches a, - and z literally, while charIn`a-z` matches alphabets from a to z.

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Apart from -, ^ and ] are also escaped in the character class, so you cannot negate a charIn via a ^ character (you should use notCharIn), and you cannot close a character class prematurely.

Backslashes \ are only escaped at the end of a string, so you can use escape sequences such as \uffff and \xff freely. If you want to include \ in the character class, you should write it at the end of a string or escape with \\.

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Additionally, charIn allows you to merge character classes by simply passing in a charIn or charRange token. For example:

const symbols = charIn`-_*$`; // the character class to be merged must not be negated (cannot be notCharIn or notCharRange)
const alphabet = charRange`a``z`;
const specialWord = charIn`0-9`(alphabet)(symbols);
const specialWord2 = charIn`0-9${alphabet}${symbols}`;
const notSpecialWord = notCharIn`0-9`(alphabet)(symbols);