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• 描述
• 构造函数
• 静态特性
• 实例特性
• 实例方法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

RegExp 对象被用于匹配文本采用模式。

For an introduction to regular expressions, read the Regular Expressions chapter 在 JavaScript 指南 .

描述

文字表示法和构造函数

There are two ways to create a RegExp object: a literal notation 和 构造函数 .

• The literal notation's parameters are enclosed between slashes and do not use quotation marks.
• The constructor function's parameters are not enclosed between slashes but do use quotation marks.

The following three expressions create the same regular expression:

/ab+c/i
new RegExp(/ab+c/, 'i') // literal notation
new RegExp('ab+c', 'i') // constructor
					

The literal notation results in compilation of the regular expression when the expression is evaluated. Use literal notation when the regular expression will remain constant. For example, if you use literal notation to construct a regular expression used in a loop, the regular expression won't be recompiled on each iteration.

The constructor of the regular expression object—for example, new RegExp('ab+c') —results in 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 obtain it from another source, such as user input.

Flags in constructor

Starting with ECMAScript 6, new RegExp(/ab+c/, 'i') no longer throws a TypeError ( "can't supply flags when constructing one RegExp from another" ) when the first argument is a RegExp and the second flags argument is present. A new RegExp from the arguments is created instead.

When using the constructor function, the normal string escape rules (preceding special characters with \ when included in a string) are necessary.

For example, the following are equivalent:

let re = /\w+/
let re = new RegExp('\\w+')
					

Perl-like RegExp properties

Note that several of the RegExp properties have both long and short (Perl-like) names. Both names always refer to the same value. (Perl is the programming language from which JavaScript modeled its regular expressions.). See also 弃用 RegExp 特性。

构造函数

RegExp()

创建新的 RegExp 对象。

静态特性

get RegExp[@@species]

The constructor function that is used to create derived objects.

RegExp.lastIndex

The index at which to start the next match.

实例特性

RegExp.prototype.flags

A string that contains the flags of the RegExp 对象。

RegExp.prototype.dotAll

Whether . matches newlines or not.

RegExp.prototype.global

Whether to test the regular expression against all possible matches in a string, or only against the first.

RegExp.prototype.ignoreCase

Whether to ignore case while attempting a match in a string.

RegExp.prototype.multiline

Whether or not to search in strings across multiple lines.

RegExp.prototype.source

The text of the pattern.

RegExp.prototype.sticky

Whether or not the search is sticky.

RegExp.prototype.unicode

Whether or not Unicode features are enabled.

实例方法

RegExp.prototype.compile()

(Re-)compiles a regular expression during execution of a script.

RegExp.prototype.exec()

Executes a search for a match in its string parameter.

RegExp.prototype.test()

Tests for a match in its string parameter.

RegExp.prototype.toString()

Returns a string representing the specified object. Overrides the Object.prototype.toString() 方法。

RegExp.prototype[@@match]()

Performs match to given string and returns match result.

RegExp.prototype[@@matchAll]()

Returns all matches of the regular expression against a string.

RegExp.prototype[@@replace]()

Replaces matches in given string with new substring.

RegExp.prototype[@@search]()

Searches the match in given string and returns the index the pattern found in the string.

RegExp.prototype[@@split]()

Splits given string into an array by separating the string into substrings.

范例

Using a regular expression to change data format

The following script uses the replace() 方法在 String instance to match a name in the format first last and output it in the format last, first .

In the replacement text, the script uses $1 and $2 to indicate the results of the corresponding matching parentheses in the regular expression pattern.

let re = /(\w+)\s(\w+)/
let str = 'John Smith'
let newstr = str.replace(re, '$2, $1')
console.log(newstr)
					

This displays "Smith, John" .

Using regular expression to split lines with different line endings/ends of line/line breaks

The default line ending varies depending on the platform (Unix, Windows, etc.). The line splitting provided in this example works on all platforms.

let text = 'Some text\nAnd some more\r\nAnd yet\rThis is the end'
let lines = text.split(/\r\n|\r|\n/)
console.log(lines) // logs [ 'Some text', 'And some more', 'And yet', 'This is the end' ]
					

Note that the order of the patterns in the regular expression matters.

Using regular expression on multiple lines

let s = 'Please yes\nmake my day!'
s.match(/yes.*day/);
// Returns null
s.match(/yes[^]*day/);
// Returns ["yes\nmake my day"]
					

Using a regular expression with the sticky flag

sticky flag indicates that the regular expression performs sticky matching in the target string by attempting to match starting at RegExp.prototype.lastIndex .

let str = '#foo#'
let regex = /foo/y
regex.lastIndex = 1
regex.test(str)      // true
regex.lastIndex = 5
regex.test(str)      // false (lastIndex is taken into account with sticky flag)
regex.lastIndex      // 0 (reset after match failure)
					

The difference between the sticky flag and the global flag

With the sticky flag y , the next match has to happen at the lastIndex position, while with the global flag g , the match can happen at the lastIndex position or later:

re = /\d/y;
while (r = re.exec("123 456")) console.log(r, "AND re.lastIndex", re.lastIndex);
// [ '1', index: 0, input: '123 456', groups: undefined ] AND re.lastIndex 1
// [ '2', index: 1, input: '123 456', groups: undefined ] AND re.lastIndex 2
// [ '3', index: 2, input: '123 456', groups: undefined ] AND re.lastIndex 3
//   ... and no more match.
					

With the global flag g , all 6 digits would be matched, not just 3.

正则表达式和 Unicode 字符

\w and \W only matches ASCII based characters; for example, a to z , A to Z , 0 to 9 ，和 _ .

To match characters from other languages such as Cyrillic or Hebrew, use \u hhhh , where hhhh is the character's Unicode value in hexadecimal.

This example demonstrates how one can separate out Unicode characters from a word.

let text = 'Образец text на русском языке'
let regex = /[\u0400-\u04FF]+/g
let match = regex.exec(text)
console.log(match[0])        // logs 'Образец'
console.log(regex.lastIndex) // logs '7'
let match2 = regex.exec(text)
console.log(match2[0])       // logs 'на' [did not log 'text']
console.log(regex.lastIndex) // logs '15'
// and so on
					

Unicode 特性转义 feature introduces a solution, by allowing for a statement as simple as \p{scx=Cyrl} .

从 URL 提取子域名

let url = 'http://xxx.domain.com'
console.log(/[^.]+/.exec(url)[0].substr(7)) // logs 'xxx'
					

Instead of using regular expressions for parsing URLs, it is usually better to use the browsers built-in URL parser by using the URL API .

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

图例

完整支持

完整支持

不支持

不支持

非标。预期跨浏览器支持较差。

弃用。不要用于新网站。

弃用。不要用于新网站。

见实现注意事项。

用户必须明确启用此特征。

用户必须明确启用此特征。

Firefox-specific notes

Starting with Firefox 34, in the case of a capturing group with quantifiers preventing its exercise, the matched text for a capturing group is now undefined instead of an empty string:

// Firefox 33 or older
'x'.replace(/x(.)?/g, function(m, group) {
  console.log("'group:" + group + "'");
});
// 'group:'
// Firefox 34 or newer
'x'.replace(/x(.)?/g, function(m, group) {
  console.log("'group:" + group + "'");
});
// 'group:undefined'
												

Note that due to web compatibility, RegExp. $N will still return an empty string instead of undefined ( bug 1053944 ).

另请参阅

• 正则表达式 chapter in the JavaScript 指南
• String.prototype.match()
• String.prototype.replace()
• String.prototype.split()

元数据

• 最后修改： Aug 17, 2020

相关话题

1. 标准内置对象
2. RegExp
3. 特性
   1. RegExp.$1-$9
   2. RegExp.input ($_)
   3. RegExp.lastMatch ($&)
   4. RegExp.lastParen ($+)
   5. RegExp.leftContext ($`)
   6. RegExp.prototype.dotAll
   7. RegExp.prototype.flags
   8. RegExp.prototype.global
   9. RegExp.prototype.ignoreCase
   10. RegExp.prototype.multiline
   11. RegExp.prototype.source
   12. RegExp.prototype.sticky
   13. RegExp.prototype.unicode
   14. RegExp.rightContext ($')
   15. RegExpInstance.lastIndex
   16. get RegExp[@@species]
4. 方法
   1. RegExp.prototype.compile()
   2. RegExp.prototype.exec()
   3. RegExp.prototype.test()
   4. RegExp.prototype.toSource()
   5. RegExp.prototype.toString()
   6. RegExp.prototype[@@matchAll]()
   7. RegExp.prototype[@@match]()
   8. RegExp.prototype[@@replace]()
   9. RegExp.prototype[@@search]()
   10. RegExp.prototype[@@split]()
5. 继承：
6. Function
7. 特性
   1. Function.arguments
   2. Function.caller
   3. Function.displayName
   4. Function.length
   5. Function.name
8. 方法
   1. Function.prototype.apply()
   2. Function.prototype.bind()
   3. Function.prototype.call()
   4. Function.prototype.toSource()
   5. Function.prototype.toString()
9. Object
10. 特性
    1. Object.prototype.__proto__
    2. Object.prototype.constructor
11. 方法
    1. Object.prototype.__defineGetter__()
    2. Object.prototype.__defineSetter__()
    3. Object.prototype.__lookupGetter__()
    4. Object.prototype.__lookupSetter__()
    5. Object.prototype.hasOwnProperty()
    6. Object.prototype.isPrototypeOf()
    7. Object.prototype.propertyIsEnumerable()
    8. Object.prototype.toLocaleString()
    9. Object.prototype.toSource()
    10. Object.prototype.toString()
    11. Object.prototype.valueOf()
    12. Object.setPrototypeOf()