6个常用的正则表达式.md

6 个常用的正则表达式

本文译自 6 JavaScript Regular Expression features you can use today

正则表达式虽然非常强大，但众所周知很难掌握。这里有 6 个有用的特性，可以帮助你开始在你的 JavaScript 项目中使用它们：

捕获组

捕获组允许您获取匹配字符串的特定部分，只需将部分正则表达式括在括号中即可 (...)：

const str = 'JavaScript is a programming language'
;/(JavaScript) is a (.*)/.exec(str)
/*
  [
    0: 'JavaScript is a programming language',
    1: 'JavaScript',
    2: 'programming language'
    ...
  ]
*/

非捕获组

非捕获组用于匹配某些内容而不捕获它，例如您并不真正需要的一个 / 或匹配组。它们的定义类似于捕获组，但前缀为 ?:：

const str = 'JavaScript is a programming language'
;/(?:JavaScript|Python) is a (.+)/.exec(str)
/*
  [
    0: 'JavaScript is a programming language',
    1: 'programming language'
    ...
  ]
*/

命名捕获组

命名捕获组允许您命名捕获组，通过在它前面加上前缀 <name>：

const str = 'JavaScript is a programming language'
;/(?<subject>.+) is a (?<description>.+)/.exec(str)
/*
  [
    0: 'JavaScript is a programming language',
    1: 'JavaScript',
    2: 'programming language',
    groups: {
      subject: 'JavaScript,
      description: 'programming language'
    }
    ...
  ]
*/

捕获组反向引用

反向引用帮你写较短的正则表达式，通过重复现有的捕获组，使用 \1，\2 等等。同样地，你也可以重复命名捕捉使用群体 \k <name>：

const str =
  'JavaScript is a programming language - an awesome programming language JavaScript is'
;/(.+) is a (?<description>.+) - an awesome \k<description> \1 is/.exec(str)
/*
  [
    0: 'JavaScript is a programming language - an awesome programming language JavaScript is',
    1: 'JavaScript',
    2: 'programming language',
    groups: {
      description: 'programming language'
    }
    ...
  ]
*/

前瞻

前瞻（Lookaheads）允许您检查某些内容是否遵循特定模式，而无需实际匹配它。您可以使用以下方法创建正先行断言（?=）和负先行断言（?!）：

const str = 'JavaScript is not the same as Java and you should remember that';
/Java(?=Script)(.*)/.exec(str)
/*
  [
    0: 'JavaScript is not the same as Java and you should remember that',
    1: 'Script is not the same as Java and you should remember that'
    ...
  ]
*/

/Java(?!Script)(.*)/.exec(str)
/*
  [
    0: 'Java and you should remember that',
    1: ' and you should remember that'
    ...
  ]
*/

Unicode 字符

最后，您可以匹配 unicode 字符，使用 /p{...} 和 /u 标志。示例包括但不限于 {Emoji}，{Math_Symbols} 和 {Script=Greek}：

const str = 'Greek looks like this: γεια'
;/\p{Script=Greek}+/u.exec(str)
/*
  [
    0: 'γεια'
    ...
  ]
*/