Viewing: developer.mozilla.org

JavaScript

js
```
const re = /ab+c/;
```
RegExp
js
```
const re = new RegExp("ab+c");
```

/abc/ /ab*c/ /Chapter (\d+)\.\d*/

/abc/ "abc" "Hi, do you know your abc's?" "The latest airplane designs evolved from slabcraft." "abc" "Grab crab" "ab c" "abc"

1 b 1 "a" 0 "b" "c" /ab*c/ "b" * 0 "cbbabbbbcdebc" "abbbbc"


/
`[xyz]`, `[^xyz]`, `.`, `\d`, `\D`, `\w`, `\W`, `\s`, `\S`, `\t`, `\r`, `\n`, `\v`, `\f`, `[\b]`, `\0`, `\cX`, `\xhh`, `\uhhhh`, `\u{hhhh}`, `x\|y`
`^`, `$`, `\b`, `\B`, `x(?=y)`, `x(?!y)`, `(?<=y)x`, `(?<!y)x`
`(x)`, `(?<Name>x)`, `(?:x)`, `\n`, `\k<Name>`
`x*`, `x+`, `x?`, `x{n}`, `x{n,}`, `x{n,m}`

( "*" ) "a" "*" "b" /a\*b/ "*"

: /a[*]b/

("/") "/example/" 1 /\/example\/[a-z]+/i

"C:\" "C" /[A-Z]:\\/

RegExp /a\*b/ new RegExp("a\\*b") "a" "*" "b"

RegExp.escape() new RegExp(RegExp.escape("a*b")) "a*b"

JavaScript

RegExp test() exec() String match()matchAll()replace()replaceAll(), search()split()


`exec()`	`null`
`test()`	`true` `false`
`match()`	`null`
`matchAll()`
`search()`	`-1`
`replace()`
`replaceAll()`
`split()`

test() search() exec() match() exec() match() RegExp exec null false

exec()

const myRe = /d(b+)d/g;
const myArray = myRe.exec("cdbbdbsbz");

myArray

const myArray = /d(b+)d/g.exec("cdbbdbsbz");
// 'cdbbdbsbz'.match(/d(b+)d/g) 
// 'cdbbdbsbz'.match(/d(b+)d/g)  [ "dbbd" ] 
// /d(b+)d/g.exec('cdbbdbsbz')  [ 'dbbd', 'bb', index: 1, input: 'cdbbdbsbz' ]

exec()

const myRe = new RegExp("d(b+)d", "g");
const myArray = myRe.exec("cdbbdbsbz");



`myArray`			`['dbbd', 'bb', index: 1, input: 'cdbbdbsbz']`
	`index`	0	`1`
	`input`		`'cdbbdbsbz'`
	`[0]`		`'dbbd'`
`myRe`	`lastIndex`	g	`5`
`myRe`	`source`		`'d(b+)d'`

const myRe = /d(b+)d/g;
const myArray = myRe.exec("cdbbdbsbz");
console.log(`lastIndex  ${myRe.lastIndex} `);

// "lastIndex  5 "

const myArray = /d(b+)d/g.exec("cdbbdbsbz");
console.log(`lastIndex  ${/d(b+)d/g.lastIndex} `);

// "lastIndex  0 "

2 /d(b+)d/g lastIndex


`d`		`hasIndices`
`g`		`global`
`i`		`ignoreCase`
`m`	`^` `$`	`multiline`
`s`	`.`	`dotAll`
`u`	"unicode" Unicode	`unicode`
`v`	Unicode `u`	`unicodeSets`
`y`	(sticky)	`sticky`

const re = /pattern/flags;

const re = new RegExp("pattern", "flags");

re = /\w+\s/g 1

const re = /\w+\s/g;
const str = "fee fi fo fum";
const myArray = str.match(re);
console.log(myArray);

// ["fee ", "fi ", "fo "]

const re = /\w+\s/g;

const re = new RegExp("\\w+\\s", "g");

m m ^ $

i, m, s

exec()

RegExp.prototype.exec() g

const str = "fee fi fo fum";
const re = /\w+\s/g;

console.log(re.exec(str)); // ["fee ", index: 0, input: "fee fi fo fum"]
console.log(re.exec(str)); // ["fi ", index: 4, input: "fee fi fo fum"]
console.log(re.exec(str)); // ["fo ", index: 7, input: "fee fi fo fum"]
console.log(re.exec(str)); // null

String.prototype.match()

console.log(str.match(re)); // ["fee ", "fi ", "fo "]

Unicode

u "unicode" Unicode Unicode Unicode Unicode

/\p{L}*/u;

Unicode RegExp.prototype.unicode

exec()test()match()matchAll()search()replace()split()

[] ()

: ^
3 \d{3} | $ 3 \d{3} $ (?:)
1 ()
3 \d{3}
() \1
4 \d{4}
: $

HTML

html

<p>
   "" 
  <br />
   ###-###-#### 
</p>
<form id="form">
  <input id="phone" />
  <button type="submit"></button>
</form>
<p id="output"></p>

JavaScript

const form = document.querySelector("#form");
const input = document.querySelector("#phone");
const output = document.querySelector("#output");

const re = /^(?:\d{3}|\(\d{3}\))([-/.])\d{3}\1\d{4}$/;

function testInfo(phoneInput) {
  const ok = re.exec(phoneInput.value);

  output.textContent = ok
    ? ` ${ok[0]}`
    : `${phoneInput.value} `;
}

form.addEventListener("submit", (event) => {
  event.preventDefault();
  testInfo(input);
});

RegExr
Regex tester: /
Regex interactive tutorial
Regex visualizer

MDN

MDN 2026317

GitHub