RegExp.prototype.test()

The test() method executes a search for a match between a regular expression and a specified string. Returns true or false.

Syntax

regexObj.test(str)

Parameters

str
The string against which to match the regular expression.

Returns

true if there is a match between the regular expression and the string str. Otherwise, false.

Description

Use test() whenever you want to know whether a pattern is found in a string. test() returns a boolean, unlike the String.prototype.search() method (which returns the index of a match, or -1 if not found).

To get more information (but with slower execution), use the exec() method. (This is similar to the String.prototype.match() method.)

As with exec() (or in combination with it), test() called multiple times on the same global regular expression instance will advance past the previous match.

Examples

Using test()

Simple example that tests if "hello" is contained at the very beginning of a string, returning a boolean result.

const str = 'hello world!';
const result = /^hello/.test(str);

console.log(result); // true

The following example logs a message which depends on the success of the test:

function testInput(re, str) {
  let midstring;
  if (re.test(str)) {
    midstring = 'contains';
  } else {
    midstring = 'does not contain';
  }
  console.log(`${str} ${midstring} ${re.source}`);
}

Using test() on a regex with the "global" flag

When a regex has the global flag set, test() will advance the lastIndex of the regex. (RegExp.prototype.exec() also advances the lastIndex property.)

Further calls to test(str) will resume searching str starting from lastIndex. The lastIndex property will continue to increase each time test() returns true

Note: As long as test() returns truelastIndex will not reset—even when testing a different string!

When test() returns false, the calling regex's lastIndex property will reset to 0.

The following example demonstrates this behaviour:

const regex = /foo/g; // the "global" flag is set

// regex.lastIndex is at 0
regex.test('foo')     // true

// regex.lastIndex is now at 3
regex.test('foo')     // false

// regex.lastIndex is at 0
regex.test('barfoo')  // true

// regex.lastIndex is at 6
regex.test('foobar')  //false

// regex.lastIndex is at 0
// (...and so on)

Specifications

Specification
ECMAScript (ECMA-262)
The definition of 'RegExp.test' in that specification.

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
testChrome Full support 1Edge Full support 12Firefox Full support 1IE Full support 4Opera Full support 5Safari Full support 1WebView Android Full support 1Chrome Android Full support 18Firefox Android Full support 4Opera Android Full support 10.1Safari iOS Full support 1Samsung Internet Android Full support 1.0nodejs Full support Yes

Legend

Full support  
Full support

See also