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

Substitution

Processing...

Code Generator

Language

Generated Code

const regex = /\b(?=0?(?:(?:4|6|9|11)\/(?:[0-2]?\d|30)|(?:[13578]|1[02])\/(?:[0-2]?\d|3[01])|(?:2)\/(?:[0-2]?\d))\b)(?:(\d)|(\d{2}))\/(?:(\d)|(\d{2}))\/(?:(\d{2})|(\d{4}))\b/g; // Alternative syntax using RegExp constructor // const regex = new RegExp('\\b(?=0?(?:(?:4|6|9|11)\\\/(?:[0-2]?\\d|30)|(?:[13578]|1[02])\\\/(?:[0-2]?\\d|3[01])|(?:2)\\\/(?:[0-2]?\\d))\\b)(?:(\\d)|(\\d{2}))\\\/(?:(\\d)|(\\d{2}))\\\/(?:(\\d{2})|(\\d{4}))\\b', 'g') const str = `MATCH: 3/26/24 11/26/24 1/2/03 4/05/2006 12/31/1600 2/29/24 10/31/20 04/30/30 NO MATCH: 13/2/55 10/32/20 2/30/24 4/31/30`; const subst = `${5:+20$5:$6}-${1:+0$1:$2}-${3:+0$3:$4}`; // 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