JavaScript RegExp Non-Whitespace Metacharacter (\S)

What Is \S?

\S matches any single character that is not whitespace. It is the opposite of \s and equals [^\s] in ordinary JavaScript regex.

\s  → one whitespace (space, tab, newline, …)
\S  → one non-whitespace (everything else)
\S+ → one or more non-whitespace (a “token”)

/\S/.test("   ")     → false
/\S/.test("  hi  ")  → true
"a  b".match(/\S+/g) → ["a", "b"]

How to Use \S

Use \S when you care about “visible” characters — detect them, tokenize them, or require them.

1. Write /\S/ to match one non-whitespace character.
2. Add + for a run of visible characters (\S+) — useful for tokens/words.
3. Use the g flag with match to collect every token.
4. Prefer \s when you want spaces; prefer \S when you want everything else.

Pseudocode

pattern has "\S"
read next character ch from the string

if ch is whitespace (space, tab, \n, \r, \f, …):
    fail this path
else:
    accept ch as a non-whitespace match

common actions:
  test(str)           → true if any visible char exists
  match(/\S+/g)       → tokens between whitespace
  /^\S+$/.test(str)   → no whitespace anywhere

Cheat Sheet

Keep these facts handy while tokenizing and validating text.

Live Preview

Run common \S operations on sample strings.

text = "   "
/\S/.test(text)
→ false

/* only whitespace — no visible character */

JavaScript Examples

Short, copy-ready snippets. Open DevTools Console, or use Try It Yourself for a live editor.

console.log(/\S/.test("   "));     // false
console.log(/\S/.test("hello"));   // true
console.log(/\S/.test("  hi  "));  // true

false
true
true

const messy = "  hello   world\tfoo  ";
console.log(messy.match(/\S+/g));
// ["hello", "world", "foo"]

const line = "Price: $19  today";
console.log(line.match(/\S+/g));
// ["Price:", "$19", "today"]

["hello", "world", "foo"]
["Price:", "$19", "today"]

const noSpaces = /^\S+$/;

console.log(noSpaces.test("username"));   // true
console.log(noSpaces.test("user_name"));  // true
console.log(noSpaces.test("user name"));  // false
console.log(noSpaces.test("   "));        // false

true
true
false
false

Performance Notes

Character-class style matches are cheap. Prefer \s when you want whitespace itself, and \S when you want the visible parts.

Key Takeaways