Regular Expressions 101

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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

/
/
g

Test String

Code Generator

Language

Generated Code

const regex = /(?P<datetime>\d{2}\/\d{2}\/\d{2} \d{2}:\d{2}:\d{2}): (?P<name>\w+(?::\s*\w+)*|[\w\s]+?)(?:\s+(?P<action>joined|left|was removed|changed the (?:subject to “\w+”|group icon))|:\s(?P<message>(?:.+|\n(?!\n))+))/g; // Alternative syntax using RegExp constructor // const regex = new RegExp('(?P<datetime>\\d{2}\\\/\\d{2}\\\/\\d{2} \\d{2}:\\d{2}:\\d{2}): (?P<name>\\w+(?::\\s*\\w+)*|[\\w\\s]+?)(?:\\s+(?P<action>joined|left|was removed|changed the (?:subject to “\\w+”|group icon))|:\\s(?P<message>(?:.+|\\n(?!\\n))+))', 'g') const str = `29/03/14 15:48:05: John Smith changed the subject to “Test” 29/03/14 16:10:39: John Smith joined 29/03/14 16:10:40: Person:2 joined 29/03/14 16:10:40: John Smith: Hello! 29/03/14 16:11:40: Person:2: some random words, 29/03/14 16:12:40: Person3 joined 29/03/14 16:13:40: John: Smith: Hello!Test message with newline Another line of the same message Another line. 29/03/14 16:14:43: Person:2: Test message using as last word joined 29/03/14 16:15:57: Person3 left 29/03/14 16:17:16: Person3 joined 29/03/14 16:18:21: Person:2 changed the group icon 29/03/14 16:19:16: Person3 was removed 29/03/14 16:20:43: Person:2: Test message using as last word left`; // Reset `lastIndex` if this regex is defined globally // regex.lastIndex = 0; let m; while ((m = regex.exec(str)) !== null) { // This is necessary to avoid infinite loops with zero-width matches if (m.index === regex.lastIndex) { regex.lastIndex++; } // The result can be accessed through the `m`-variable. m.forEach((match, groupIndex) => { console.log(`Found match, group ${groupIndex}: ${match}`); }); }

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