String.prototype.matchAll() - JavaScript 编辑

The matchAll() method returns an iterator of all results matching a string against a regular expression, including capturing groups.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

Syntax

str.matchAll(regexp)

Parameters

regexp

A regular expression object.

If a non-RegExp object obj is passed, it is implicitly converted to a RegExp by using new RegExp(obj).

The RegExp object must have the /g flag, otherwise a TypeError will be thrown.

Return value

An iterator (which is not a restartable iterable).

Examples

Regexp.exec() and matchAll()

Prior to the addition of matchAll to JavaScript, it was possible to use calls to regexp.exec (and regexes with the /g flag) in a loop to obtain all the matches:

const regexp = RegExp('foo[a-z]*','g');
const str = 'table football, foosball';
let match;

while ((match = regexp.exec(str)) !== null) {
  console.log(`Found ${match[0]} start=${match.index} end=${regexp.lastIndex}.`);
  // expected output: "Found football start=6 end=14."
  // expected output: "Found foosball start=16 end=24."
}

With matchAll available, you can avoid the while loop and exec with g.

Instead, by using matchAll, you get an iterator to use with the more convenient for...of, array spread, or Array.from() constructs:

const regexp = RegExp('foo[a-z]*','g');
const str = 'table football, foosball';
const matches = str.matchAll(regexp);

for (const match of matches) {
  console.log(`Found ${match[0]} start=${match.index} end=${match.index + match[0].length}.`);
}
// expected output: "Found football start=6 end=14."
// expected output: "Found foosball start=16 end=24."

// matches iterator is exhausted after the for..of iteration
// Call matchAll again to create a new iterator
Array.from(str.matchAll(regexp), m => m[0]);
// Array [ "football", "foosball" ]

matchAll will throw an exception if the g flag is missing.

const regexp = RegExp('[a-c]','');
const str = 'abc';
str.matchAll(regexp);
// TypeError

matchAll internally makes a clone of the regexp—so, unlike regexp.exec(), lastIndex does not change as the string is scanned.

const regexp = RegExp('[a-c]','g');
regexp.lastIndex = 1;
const str = 'abc';
Array.from(str.matchAll(regexp), m => `${regexp.lastIndex} ${m[0]}`);
// Array [ "1 b", "1 c" ]

Better access to capturing groups (than String.prototype.match())

Another compelling reason for matchAll is the improved access to capture groups.

Capture groups are ignored when using match() with the global /g flag:

let regexp = /t(e)(st(\d?))/g;
let str = 'test1test2';

str.match(regexp);
// Array ['test1', 'test2']

Using matchAll, you can access capture groups easily:

let array = [...str.matchAll(regexp)];

array[0];
// ['test1', 'e', 'st1', '1', index: 0, input: 'test1test2', length: 4]
array[1];
// ['test2', 'e', 'st2', '2', index: 5, input: 'test1test2', length: 4]

Specifications

Specification
ECMAScript (ECMA-262) The definition of 'String.prototype.matchAll' in that specification.

Browser compatibility

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The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

See also

• String.prototype.match()
• Using regular expressions in JavaScript
• Capturing groups
• RegExp
• RegExp.prototype.exec()
• RegExp.prototype.test()