Regular Expressions 101

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  • Substitution
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  • Unit Tests (2)

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

/
/
gm

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

const regex = /(?<!(?:\\{2})*\\)(?:(?<begin_capture>[\(])(?<begin_capture_modifier>(?=[<][a-z_A-Z]+[>])|(?!\?(?:<?[=!]|:)))|(?<begin_non_capture>\((?=\?(?:<?[=!]|:))))|(?:(?<end>\)))/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('(?<!(?:\\\\{2})*\\\\)(?:(?<begin_capture>[\\(])(?<begin_capture_modifier>(?=[<][a-z_A-Z]+[>])|(?!\\?(?:<?[=!]|:)))|(?<begin_non_capture>\\((?=\\?(?:<?[=!]|:))))|(?:(?<end>\\)))', 'gm') const str = `// Basic - Repeat Delimiters /^((?:([gimsuy])(?!.*\\\\2))*)/gm // Basic - Nested - Captured | Non-captured ^(?:(// +)(?:(@noframes)([ \\t]*\$)|(@(?:include|match|grant|require))([\\t ]+)(?:(https?.+?)|(.+))(\\**)([ \\t]*)|(^//[ \\t]+)(@(?:author|name(?:space)?|version|description))([ \\t]+)(.+?)([ \\t]*)|(^//[ \\t]+)(@resource)([ \\t]+)(\\S+)([ \\t]+)(\\S+)([ \\t]*))(\\n(?://[ \\t]*\\n)*)) // Basic - Captured | Non-captured | Lookbehind Positive (?<=^[ \\t]*)(//)([ ])(?<capture_name>)(Case:)([ \\t]+)(.*\\S)([ \\t]*)?\$ // Complex (?<=^[ \\t]*)(//)([ ])(Case:)([ \\t]+)(.*\\S)([ \\t]*)?\$ ^(?:(?:(?:[0]*|[0]*1)(?=\$))|(?:(?:[0]*|[0]*1(?[1-9]+)))?[\\.][\\d]+)\$ ^((?:[ ]{2})*[ ])([#])([ ]+)(?:(@param)([ ]+)(?:([\\\$][\\d\\*@\$?&]+))(\\??)(?:(:)([\\t ]+)(\\w+))?(?:([ ]+)([=][>])([ ]+)(?:([A-Za-z_-](?:[<][^\\n>]+[>]|[A-Za-z_-]*[^\\n]*?))(?:([ ]+)(?:(@desc)|([<]\\?))([ ]+)(.+?))?))([ ]*)|(@return)(?:([ ]+)([=][>])([ ]+)(?:([A-Za-z_][A-Za-z_]*)(.*?)(?:([ ]+)(?:(@desc)|([<]\\?))([ ]+)(.+?))?)))\$`; const subst = `\n - $begin_capture`; // The substituted value will be contained in the result variable const result = str.replace(regex, subst); console.log('Substitution result: ', result);

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions