正则表达式 | JavaScript

Regular expressions are patterns used to match character combinations in strings. In JavaScript, regular expressions are also objects. These patterns are used with the exec() and test() methods of RegExp , and with the match() , matchAll() , replace() , replaceAll() , search() ，和 split() methods of String . This chapter describes JavaScript regular expressions.

创建正则表达式

You construct a regular expression in one of two ways:

Using a regular expression literal, which consists of a pattern enclosed between slashes, as follows:
```
let re = /ab+c/;
							
```
Regular expression literals provide compilation of the regular expression when the script is loaded. If the regular expression remains constant, using this can improve performance.
Or calling the constructor function of the RegExp object, as follows:
```
let re = new RegExp('ab+c');
							
```
Using the constructor function provides runtime compilation of the regular expression. Use the constructor function when you know the regular expression pattern will be changing, or you don't know the pattern and are getting it from another source, such as user input.

编写正则表达式模式

A regular expression pattern is composed of simple characters, such as /abc/ , or a combination of simple and special characters, such as /ab*c/ or /Chapter (\d+)\.\d*/ . The last example includes parentheses, which are used as a memory device. The match made with this part of the pattern is remembered for later use, as described in Using groups .

注意： If you are already familiar with the forms of a regular expression, you may also read the cheatsheet for a quick lookup for a specific pattern/construct.

使用简单模式

Simple patterns are constructed of characters for which you want to find a direct match. For example, the pattern /abc/ matches character combinations in strings only when the exact sequence "abc" occurs (all characters together and in that order). Such a match would succeed in the strings "Hi, do you know your abc's?" and "The latest airplane designs evolved from slabcraft." In both cases the match is with the substring "abc" . There is no match in the string "Grab crab" because while it contains the substring "ab c" , it does not contain the exact substring "abc" .

使用特殊字符

When the search for a match requires something more than a direct match, such as finding one or more b's, or finding white space, you can include special characters in the pattern. For example, to match a single "a" followed by zero or more "b" s followed by "c" , you'd use the pattern /ab*c/ : the * after "b" means "0 or more occurrences of the preceding item." In the string "cbbabbbbcdebc" , this pattern will match the substring "abbbbc" .

The following pages provide lists of the different special characters that fit into each category, along with descriptions and examples.

断言
字符类
Groups and ranges
量词
Unicode 特性转义

If you want to look at all the special characters that can be used in regular expressions in a single table, see the following:

Special characters in regular expressions.
字符/构造	Corresponding article
`\` , `.` , `\cX` , `\d` , `\D` , `\f` , `\n` , `\r` , `\s` , `\S` , `\t` , `\v` , `\w` , `\W` , `\0` , `\xhh` , `\uhhhh` , `\uhhhhh` , `[\b]`	字符类
`^` , `$` , `x(?=y)` , `x(?!y)` , `(?<=y)x` , `(?<!y)x` , `\b` , `\B`	断言
`(x)` , `(?:x)` , `(?<Name>x)` , `x\|y` , `[xyz]` , `[^xyz]` , `\ Number`	Groups and ranges
`*` , `+` , `?` , `x{ n }` , `x{ n ,}` , `x{ n , m }`	量词
`\p{ UnicodeProperty }` , `\P{ UnicodeProperty }`	Unicode 特性转义

注意： A larger cheatsheet is also available (only aggregating parts of those individual articles).

Escaping

If you need to use any of the special characters literally (actually searching for a "*" , for instance), you must escape it by putting a backslash in front of it. For instance, to search for "a" followed by "*" followed by "b" , you'd use /a\*b/ — the backslash "escapes" the "*" , making it literal instead of special.

Similarly, if you're writing a regular expression literal and need to match a slash ("/"), you need to escape that (otherwise, it terminates the pattern). For instance, to search for the string "/example/" followed by one or more alphabetic characters, you'd use /\/example\/[a-z]+/i —the backslashes before each slash make them literal.

To match a literal backslash, you need to escape the backslash. For instance, to match the string "C:\" where "C" can be any letter, you'd use /[A-Z]:\\/ — the first backslash escapes the one after it, so the expression searches for a single literal backslash.

If using the RegExp constructor with a string literal, remember that the backslash is an escape in string literals, so to use it in the regular expression, you need to escape it at the string literal level. /a\*b/ and new RegExp("a\\*b") create the same expression, which searches for "a" followed by a literal "*" followed by "b".

If escape strings are not already part of your pattern you can add them using String.replace :

function escapeRegExp(string) {
  return string.replace(/[.*+\-?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string
}

The "g" after the regular expression is an option or flag that performs a global search, looking in the whole string and returning all matches. It is explained in detail below in Advanced Searching With Flags .

Why isn't this built into JavaScript? There is a proposal to add such a function to RegExp, but it was rejected by TC39.

Using parentheses

Parentheses around any part of the regular expression pattern causes that part of the matched substring to be remembered. Once remembered, the substring can be recalled for other use. See Groups and ranges 了解更多细节。

在 JavaScript 中使用正则表达式

Regular expressions are used with the RegExp methods test() and exec() and with the String methods match() , replace() , search() ，和 split() . These methods are explained in detail in the JavaScript 参考 .

Methods that use regular expressions
Method	描述
`exec()`	Executes a search for a match in a string. It returns an array of information or `null` on a mismatch.
`test()`	Tests for a match in a string. It returns `true` or `false` .
`match()`	Returns an array containing all of the matches, including capturing groups, or `null` if no match is found.
`matchAll()`	Returns an iterator containing all of the matches, including capturing groups.
`search()`	Tests for a match in a string. It returns the index of the match, or `-1` if the search fails.
`replace()`	Executes a search for a match in a string, and replaces the matched substring with a replacement substring.
`replaceAll()`	Executes a search for all matches in a string, and replaces the matched substrings with a replacement substring.
`split()`	Uses a regular expression or a fixed string to break a string into an array of substrings.

When you want to know whether a pattern is found in a string, use the test() or search() methods; for more information (but slower execution) use the exec() or match() methods. If you use exec() or match() and if the match succeeds, these methods return an array and update properties of the associated regular expression object and also of the predefined regular expression object, RegExp . If the match fails, the exec() method returns null (which coerces to false ).

In the following example, the script uses the exec() method to find a match in a string.

var myRe = /d(b+)d/g;
var myArray = myRe.exec('cdbbdbsbz');

If you do not need to access the properties of the regular expression, an alternative way of creating myArray is with this script:

var myArray = /d(b+)d/g.exec('cdbbdbsbz');
    // similar to "cdbbdbsbz".match(/d(b+)d/g); however,
    // "cdbbdbsbz".match(/d(b+)d/g) outputs Array [ "dbbd" ], while
    // /d(b+)d/g.exec('cdbbdbsbz') outputs Array [ 'dbbd', 'bb', index: 1, input: 'cdbbdbsbz' ].

(见 different behaviors for further info about the different behaviors.)

If you want to construct the regular expression from a string, yet another alternative is this script:

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

With these scripts, the match succeeds and returns the array and updates the properties shown in the following table.

Results of regular expression execution.
Object	Property or index	描述	In this example
`myArray`		The matched string and all remembered substrings.	`['dbbd', 'bb', index: 1, input: 'cdbbdbsbz']`
	`index`	The 0-based index of the match in the input string.	`1`
	`input`	The original string.	`'cdbbdbsbz'`
	`[0]`	The last matched characters.	`'dbbd'`
`myRe`	`lastIndex`	The index at which to start the next match. (This property is set only if the regular expression uses the g option, described in Advanced Searching With Flags .)	`5`
`myRe`	`source`	The text of the pattern. Updated at the time that the regular expression is created, not executed.	`'d(b+)d'`

As shown in the second form of this example, you can use a regular expression created with an object initializer without assigning it to a variable. If you do, however, every occurrence is a new regular expression. For this reason, if you use this form without assigning it to a variable, you cannot subsequently access the properties of that regular expression. For example, assume you have this script:

var myRe = /d(b+)d/g;
var myArray = myRe.exec('cdbbdbsbz');
console.log('The value of lastIndex is ' + myRe.lastIndex);
// "The value of lastIndex is 5"

However, if you have this script:

var myArray = /d(b+)d/g.exec('cdbbdbsbz');
console.log('The value of lastIndex is ' + /d(b+)d/g.lastIndex);
// "The value of lastIndex is 0"

The occurrences of /d(b+)d/g in the two statements are different regular expression objects and hence have different values for their lastIndex property. If you need to access the properties of a regular expression created with an object initializer, you should first assign it to a variable.

Advanced searching with flags

Regular expressions have six optional flags that allow for functionality like global and case insensitive searching. These flags can be used separately or together in any order, and are included as part of the regular expression.

Regular expression flags
Flag	描述	Corresponding property
`g`	Global search.	`RegExp.prototype.global`
`i`	Case-insensitive search.	`RegExp.prototype.ignoreCase`
`m`	Multi-line search.	`RegExp.prototype.multiline`
`s`	Allows `.` to match newline characters.	`RegExp.prototype.dotAll`
`u`	"unicode"; treat a pattern as a sequence of unicode code points.	`RegExp.prototype.unicode`
`y`	Perform a "sticky" search that matches starting at the current position in the target string. See `sticky` .	`RegExp.prototype.sticky`

To include a flag with the regular expression, use this syntax:

var re = /pattern/flags;

var re = new RegExp('pattern', 'flags');

Note that the flags are an integral part of a regular expression. They cannot be added or removed later.

例如， re = /\w+\s/g creates a regular expression that looks for one or more characters followed by a space, and it looks for this combination throughout the string.

var re = /\w+\s/g;
var str = 'fee fi fo fum';
var myArray = str.match(re);
console.log(myArray);
// ["fee ", "fi ", "fo "]

You could replace the line:

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

with:

var re = new RegExp('\\w+\\s', 'g');

and get the same result.

The behavior associated with the g flag is different when the .exec() method is used. The roles of "class" and "argument" get reversed: In the case of .match() , the string class (or data type) owns the method and the regular expression is just an argument, while in the case of .exec() , it is the regular expression that owns the method, with the string being the argument. Contrast this str.match(re) versus re.exec(str) . The g flag is used with the .exec() method to get iterative progression.

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

m flag is used to specify that a multiline input string should be treated as multiple lines. If the m flag is used, ^ and $ match at the start or end of any line within the input string instead of the start or end of the entire string.

范例

注意： Several examples are also available in:

The reference pages for exec() , test() , match() , matchAll() , search() , replace() , split()
This guide articles': character classes , assertions , groups and ranges , quantifiers , Unicode 特性转义

Using special characters to verify input

In the following example, the user is expected to enter a phone number. When the user presses the "Check" button, the script checks the validity of the number. If the number is valid (matches the character sequence specified by the regular expression), the script shows a message thanking the user and confirming the number. If the number is invalid, the script informs the user that the phone number is not valid.

Within non-capturing parentheses (?: , the regular expression looks for three numeric characters \d{3} OR | a left parenthesis $ followed by three digits \d{3} , followed by a close parenthesis $ , (end non-capturing parenthesis ) ), followed by one dash, forward slash, or decimal point and when found, remember the character ([-\/\.]) , followed by three digits \d{3} , followed by the remembered match of a dash, forward slash, or decimal point \1 , followed by four digits \d{4} .

Change event activated when the user presses Enter sets the value of RegExp.input .

HTML

<p>
  Enter your phone number (with area code) and then click "Check".
  <br>
  The expected format is like ###-###-####.
</p>
<form action="#">
  <input id="phone">
    <button onclick="testInfo(document.getElementById('phone'));">Check</button>
</form>

JavaScript

var re = /(?:\d{3}|\(\d{3}\))([-\/\.])\d{3}\1\d{4}/;
function testInfo(phoneInput) {
  var OK = re.exec(phoneInput.value);
  if (!OK) {
    console.error(phoneInput.value + ' isn\'t a phone number with area code!');
  } else {
    console.log('Thanks, your phone number is ' + OK[0]);}
}

结果

工具

RegExr
Regex tester
Regex visualizer

规范

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

浏览器兼容性

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. 更新 GitHub 上的兼容性数据

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
`RegExp`	Chrome 1	Edge 12	Firefox 1	IE 4	Opera 5	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`RegExp()` 构造函数	Chrome 1	Edge 12	Firefox 1	IE 4	Opera 5	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`compile` 弃用	Chrome 1	Edge 12	Firefox 1	IE 4	Opera 6	Safari 3.1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 2	Samsung Internet Android 1.0	nodejs Yes
`dotAll`	Chrome 62	Edge 79	Firefox 78	IE No	Opera 49	Safari 12	WebView Android 62	Chrome Android 62	Firefox Android No	Opera Android 46	Safari iOS 12	Samsung Internet Android 8.0	nodejs 8.10.0 8.10.0 8.3.0 Disabled Disabled From version 8.3.0: this feature is behind the `--harmony` runtime flag.
`exec`	Chrome 1	Edge 12	Firefox 1	IE 4	Opera 5	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`flags`	Chrome 49	Edge 79	Firefox 37	IE No	Opera 39	Safari 9	WebView Android 49	Chrome Android 49	Firefox Android 37	Opera Android 41	Safari iOS 9	Samsung Internet Android 5.0	nodejs 6.0.0
`global`	Chrome 1	Edge 12	Firefox 1	IE 5.5	Opera 5	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`ignoreCase`	Chrome 1	Edge 12	Firefox 1	IE 5.5	Opera 5	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`RegExp.input` ( `$_` ) 非标	Chrome 1	Edge 12	Firefox 1	IE 5.5	Opera 15	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 14	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`lastIndex`	Chrome 1	Edge 12	Firefox 1	IE 5.5	Opera 5	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`RegExp.lastMatch` ( `$&` ) 非标	Chrome 1	Edge 12	Firefox 1	IE 5.5	Opera 10.5	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 11	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`RegExp.lastParen` ( `$+` ) 非标	Chrome 1	Edge 12	Firefox 1	IE 5.5	Opera 10.5	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 11	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`RegExp.leftContext` ( $` ) 非标	Chrome 1	Edge 12	Firefox 1	IE 5.5	Opera 8	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
lookbehind assertions ( `(?<= )` and `(?<! )` )	Chrome 62	Edge 79	Firefox 78	IE No	Opera 49	Safari No	WebView Android 62	Chrome Android 62	Firefox Android No No 见 bug 1225665 .	Opera Android 46	Safari iOS No	Samsung Internet Android 8.0	nodejs 8.10.0
`multiline`	Chrome 1	Edge 12	Firefox 1	IE 5.5	Opera 5	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`RegExp.$1-$9`	Chrome 1	Edge 12	Firefox 1	IE 4	Opera 5	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
Named capture groups	Chrome 64	Edge 79	Firefox 78	IE No	Opera 51	Safari 11.1	WebView Android 64	Chrome Android 64	Firefox Android No	Opera Android 47	Safari iOS 11.3	Samsung Internet Android 9.0	nodejs 10.0.0 10.0.0 8.3.0 Disabled Disabled From version 8.3.0: this feature is behind the `--harmony` runtime flag.
Unicode property escapes ( `\p{...}` )	Chrome 64	Edge 79	Firefox 78	IE No	Opera 51	Safari 11.1	WebView Android 64	Chrome Android 64	Firefox Android No	Opera Android 47	Safari iOS 11.3	Samsung Internet Android 9.0	nodejs 10.0.0 10.0.0 8.3.0 Disabled Disabled From version 8.3.0: this feature is behind the `--harmony` runtime flag.
`RegExp.rightContext` ( `$'` ) 非标	Chrome 1	Edge 12	Firefox 1	IE 5.5	Opera 8	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`source`	Chrome 1	Edge 12	Firefox 1	IE 4	Opera 5	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`sticky`	Chrome 49	Edge 13	Firefox 3	IE No	Opera 36	Safari 10	WebView Android 49	Chrome Android 49	Firefox Android 4	Opera Android 36	Safari iOS 10	Samsung Internet Android 5.0	nodejs Yes
`test`	Chrome 1	Edge 12	Firefox 1	IE 4	Opera 5	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`toSource` 非标	Chrome No	Edge No	Firefox 1 — 74 1 — 74 Starting in Firefox 74, `toSource()` is no longer available for use by web content. It is still allowed for internal and privileged code.	IE No	Opera No	Safari No	WebView Android No	Chrome Android No	Firefox Android 4	Opera Android No	Safari iOS No	Samsung Internet Android No	nodejs No
`toString`	Chrome 1	Edge 12	Firefox 1	IE 4	Opera 5	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`unicode`	Chrome 50	Edge 12 12 Case folding is implemented in version 13	Firefox 46	IE No	Opera 37	Safari 10	WebView Android 50	Chrome Android 50	Firefox Android 46	Opera Android 37	Safari iOS 10	Samsung Internet Android 5.0	nodejs Yes
`@@match`	Chrome 50	Edge 13	Firefox 49	IE No	Opera 37	Safari 10	WebView Android 50	Chrome Android 50	Firefox Android 49	Opera Android 37	Safari iOS 10	Samsung Internet Android 5.0	nodejs 6.0.0
`@@matchAll`	Chrome 73	Edge 79	Firefox 67	IE No	Opera 60	Safari 13	WebView Android 73	Chrome Android 73	Firefox Android 67	Opera Android 52	Safari iOS 13	Samsung Internet Android 5.0	nodejs 12.0.0
`@@replace`	Chrome 50	Edge 79	Firefox 49	IE No	Opera 37	Safari 10	WebView Android 50	Chrome Android 50	Firefox Android 49	Opera Android 37	Safari iOS 10	Samsung Internet Android 5.0	nodejs 6.0.0
`@@search`	Chrome 50	Edge 13	Firefox 49	IE No	Opera 37	Safari 10	WebView Android 50	Chrome Android 50	Firefox Android 49	Opera Android 37	Safari iOS 10	Samsung Internet Android 5.0	nodejs 6.0.0
`@@species`	Chrome 50	Edge 13	Firefox 49	IE No	Opera 37	Safari 10	WebView Android 50	Chrome Android 50	Firefox Android 49	Opera Android 37	Safari iOS 10	Samsung Internet Android 5.0	nodejs 6.5.0 6.5.0 6.0.0 Disabled Disabled From version 6.0.0: this feature is behind the `--harmony` runtime flag.
`@@split`	Chrome 50	Edge 79	Firefox 49	IE No	Opera 37	Safari 10	WebView Android 50	Chrome Android 50	Firefox Android 49	Opera Android 37	Safari iOS 10	Samsung Internet Android 5.0	nodejs 6.0.0

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