JS RegExp Classes

Character classes are shorthand notations that match entire categories of characters at once -- \d for any digit, \w for any word character, \s for any whitespace -- and their uppercase opposites (\D, \W, \S) match everything NOT in that category, letting you build patterns without listing every individual character.

In this page:

Digits with \d
Word Characters with \w
Whitespace with \s
Negated Classes: \D, \W, \S
Custom Character Classes with [ ]

Syntax

javascript

[abc]   [^abc]   [a-z]
\d   \w   \s
\D   \W   \S

Digits with \d

\d matches any single digit character, 0 through 9 -- \d\d\d matches exactly three consecutive digits, and \d+ (combined with a quantifier) matches one or more digits in a row, the basis for matching numbers, phone digits, or zip codes.

Note: Combine \d with quantifiers (+ for one or more, {n} for exactly n) to match multi-digit numbers rather than just a single digit.

Warning: \d alone matches exactly one digit -- forgetting a quantifier when you meant to match a multi-digit number is a very common regex mistake.

उदाहरण: Digits with \d

javascript

console.log(/\d\d\d/.test("123")); // exactly 3 digits
console.log("Phone: 12345".match(/\d+/));

Word Characters with \w

\w matches any letter (upper or lower case), digit, or underscore -- effectively the set of characters typically valid in a variable name or simple identifier -- but notably does NOT include spaces, hyphens, or most punctuation.

Note: Remember \w excludes spaces and most punctuation -- if you need to match a full name with spaces, combine \w with an explicit space character or use \s alongside it.

Warning: Using \w+ to try to match a full sentence or phrase with spaces stops at the first space, since spaces are not part of the \w character class.

उदाहरण: Word Characters with \w

javascript

console.log(/^\w+$/.test("user_1"));  // true, letters/digits/underscore
console.log(/^\w+$/.test("user 1"));  // false, contains a space

Whitespace with \s

\s matches any whitespace character -- a regular space, a tab, or a newline -- useful for splitting text on any kind of whitespace or normalizing inconsistent spacing, rather than matching only a literal space character.

Note: Use \s+ (one or more whitespace characters) rather than a literal space when normalizing or splitting text that might contain tabs or multiple consecutive spaces.

Warning: A literal space character in a pattern only matches an actual space -- it will not match a tab or newline the way \s does, which can cause a pattern to miss text formatted with different whitespace.

उदाहरण: Whitespace with \s

javascript

console.log("a\tb  c".split(/\s/)); // splits on tab and spaces alike

Negated Classes: \D, \W, \S

The uppercase versions of the shorthand classes match the exact opposite of their lowercase counterparts -- \D matches any non-digit, \W matches any non-word-character, and \S matches any non-whitespace character.

Note: Use a negated class when it is more natural to describe what you want to exclude, rather than what you want to include.

Warning: A negated class like \D still matches whitespace and punctuation, not just letters -- it only excludes digits specifically, nothing more.

उदाहरण: Negated Classes: \D, \W, \S

javascript

console.log(/\D/.test("abc"));  // true, non-digit found
console.log(/\W/.test("a_b"));  // false, only word chars/underscore
console.log(/\S/.test("  "));   // false, only whitespace

Custom Character Classes with [ ]

Square brackets define a custom character class matching any single character from the specified set -- [aeiou] matches any single vowel, and [a-z] uses a range to match any single lowercase letter, letting you build precise character sets beyond the built-in shorthand classes.

Note: Use a range like [a-z] or [0-9] for a compact way to match any character within a contiguous range, rather than listing every individual character.

Warning: A custom character class without the i flag is case-sensitive by default -- [a-z] will not match an uppercase letter unless A-Z is added or the i flag is applied.

उदाहरण: Custom Character Classes with [ ]

javascript

console.log(/[aeiou]/.test("sky"));  // false, no vowels
console.log(/[a-z]/.test("ABC1"));   // false, no lowercase letters

Live Example

Chapter Quiz — Complete all 26 topics to unlock

0/26 topics done

Complete these topics first:

← Previous Lesson JS RegExp Flags Next Lesson → JS RegExp Metachars

JS RegExp Classes

Digits with \d

Word Characters with \w

Whitespace with \s

Negated Classes: \D, \W, \S

Custom Character Classes with [ ]

Chapter Quiz — Complete all 26 topics to unlock

Login to run this code