test()?RegExp.prototype.test(string) answers one question: does this pattern match? It returns true or false — no match text, no groups. Ideal for validation and if guards.
regex.test(string) → true | false
/world/.test("hello world") → true
/world/.test("hello there") → false
/^\d+$/.test("42") → true (whole string)
/hello/i.test("HELLO") → true (ignore case)
Need match text? → use exec() or String.match()| Use | Prefer |
|---|---|
| Yes / no check | regex.test(str) |
| Match details | regex.exec(str) |
| Whole-field validation | /^…$/.test(value) |
test()Build a regex, call test with a string, and branch on the boolean.
/…/) or new RegExp(…).regex.test(string) — returns true or false.^ and $ when the entire value must match.g flag for simple checks (or reset lastIndex).| Piece | Required? | Role |
|---|---|---|
| RegExp | Yes | Pattern to test against |
string | Yes | Input to search (coerced to string) |
Flags (i, m, …) | Optional | Change matching rules; avoid g for simple checks |
regex = /pattern/
input = given string
if pattern finds a match in input:
return true
else:
return false
// with g or y flag:
// also update regex.lastIndex for the next search
// without g:
// lastIndex is not used for sticky searchingKeep these facts handy while writing boolean pattern checks.
| Topic | Detail |
|---|---|
| Syntax | regex.test(string) |
| Return | true or false only |
| Search scope | Anywhere in the string (unless anchored) |
| Whole field | /^pattern$/.test(value) |
vs exec() | Boolean vs match details |
g flag trap | Advances lastIndex on each call |
| Standard | ES3+ (universal) |
Pick a pattern and a sample string to see what test() returns.
Short, copy-ready snippets. Open DevTools Console, or use Try It Yourself for a live editor.
Test whether the word world appears in a sentence.
const regex = /world/;
console.log(regex.test("hello world")); // true
console.log(regex.test("hello there")); // false/world/ looks for that literal text."hello world" contains world → true."hello there" has no match → false.Use anchors and ! to accept or reject a whole field.
const digitsOnly = /^\d+$/;
function validateAge(value) {
if (!digitsOnly.test(value)) {
return "Age must be digits only.";
}
return "OK";
}
console.log(validateAge("42")); // OK
console.log(validateAge("42abc")); // Age must be digits only.^ and $ require every character to be a digit.!digitsOnly.test(value) is true when validation fails."42" matches → return "OK"."42abc" fails the whole-string rule → error message.lastIndexSee why repeated test() calls on a global regex can surprise you.
const regex = /a/g;
console.log(regex.test("aba")); // true — match at index 0
console.log(regex.test("aba")); // true — match at index 2
console.log(regex.test("aba")); // false — lastIndex past end
regex.lastIndex = 0;
console.log(regex.test("aba")); // true — reset worksg remembers position. Each successful test() advances lastIndex.0 and 2 in "aba".false.lastIndex = 0, or omit g for simple boolean checks.Check these before relying on test() in real projects.
g for simple boolean checksGlobal regexes update lastIndex. Prefer a non-global pattern, or reset lastIndex before each reuse. See the g modifier.
/\d+/.test("abc42") is true. Use /^\d+$/ when the whole field must be digits.
/2/.test(42) becomes a string check on "42". Pass strings explicitly when clarity matters.
test() does not return match textNeed groups or the matched substring? Use exec() or String.prototype.match.
RegExp.prototype.test() is part of core JavaScript (ES3+). It works everywhere without polyfills.
Supported in every modern and legacy browser, plus all Node.js versions. Universal boolean pattern API.
Bottom line: Safe everywhere. Prefer test() for yes/no checks; reach for exec() when you need match details.
| Approach | Cost | Best for |
|---|---|---|
regex.test(str) | Stops at first match | Validation, guards, filters |
regex.exec(str) | Builds match object | When you need groups / index |
str.match(/…/g) | Finds all matches | Collecting every hit |
For a pure boolean check, test() is the lightest choice — it can stop as soon as one match is found. Keep patterns simple and anchored when validating short form fields.
test() returns only true or false./^…$/.test(value) for whole fields.exec() instead.g for simple checks, or reset lastIndex.One line: test() is the yes/no regex tool — perfect for if guards, risky with a sticky g flag.
compile() is deprecated — read why and what to use instead.
11 people found this page helpful