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

/
/
gm

Test String

Code Generator

Language

Generated Code

const regex = /^0$|^[1-9](?:[0-9]{3}|[0-9]{19}|[0-9]{24})$|^[0-9][1-9](?:[0-9]{2}|[0-9]{18}|[0-9]{23})$|^[0-9]{2}[1-9](?:[0-9]|[0-9]{17}|[0-9]{22})$|^[0-9]{3}[1-9](?:|[0-9]{16}|[0-9]{21})$|^[0-9]{4}[1-9](?:[0-9]{15}|[0-9]{20})$|^[0-9]{5}[1-9](?:[0-9]{14}|[0-9]{19})$|^[0-9]{6}[1-9](?:[0-9]{13}|[0-9]{18})$|^[0-9]{7}[1-9](?:[0-9]{12}|[0-9]{17})$|^[0-9]{8}[1-9](?:[0-9]{11}|[0-9]{16})$|^[0-9]{9}[1-9](?:[0-9]{10}|[0-9]{15})$|^[0-9]{10}[1-9](?:[0-9]{9}|[0-9]{14})$|^[0-9]{11}[1-9](?:[0-9]{8}|[0-9]{13})$|^[0-9]{12}[1-9](?:[0-9]{7}|[0-9]{12})$|^[0-9]{13}[1-9](?:[0-9]{6}|[0-9]{11})$|^[0-9]{14}[1-9](?:[0-9]{5}|[0-9]{10})$|^[0-9]{15}[1-9](?:[0-9]{4}|[0-9]{9})$|^[0-9]{16}[1-9](?:[0-9]{3}|[0-9]{8})$|^[0-9]{17}[1-9](?:[0-9]{2}|[0-9]{7})$|^[0-9]{18}[1-9](?:[0-9]|[0-9]{6})$|^[0-9]{19}[1-9](?:|[0-9]{10})$|^[0-9]{20}[1-9][0-9]{4}$|^[0-9]{21}[1-9][0-9]{3}$|^[0-9]{22}[1-9][0-9]{2}$|^[0-9]{23}[1-9][0-9]$|^[0-9]{24}[1-9]$/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^0$|^[1-9](?:[0-9]{3}|[0-9]{19}|[0-9]{24})$|^[0-9][1-9](?:[0-9]{2}|[0-9]{18}|[0-9]{23})$|^[0-9]{2}[1-9](?:[0-9]|[0-9]{17}|[0-9]{22})$|^[0-9]{3}[1-9](?:|[0-9]{16}|[0-9]{21})$|^[0-9]{4}[1-9](?:[0-9]{15}|[0-9]{20})$|^[0-9]{5}[1-9](?:[0-9]{14}|[0-9]{19})$|^[0-9]{6}[1-9](?:[0-9]{13}|[0-9]{18})$|^[0-9]{7}[1-9](?:[0-9]{12}|[0-9]{17})$|^[0-9]{8}[1-9](?:[0-9]{11}|[0-9]{16})$|^[0-9]{9}[1-9](?:[0-9]{10}|[0-9]{15})$|^[0-9]{10}[1-9](?:[0-9]{9}|[0-9]{14})$|^[0-9]{11}[1-9](?:[0-9]{8}|[0-9]{13})$|^[0-9]{12}[1-9](?:[0-9]{7}|[0-9]{12})$|^[0-9]{13}[1-9](?:[0-9]{6}|[0-9]{11})$|^[0-9]{14}[1-9](?:[0-9]{5}|[0-9]{10})$|^[0-9]{15}[1-9](?:[0-9]{4}|[0-9]{9})$|^[0-9]{16}[1-9](?:[0-9]{3}|[0-9]{8})$|^[0-9]{17}[1-9](?:[0-9]{2}|[0-9]{7})$|^[0-9]{18}[1-9](?:[0-9]|[0-9]{6})$|^[0-9]{19}[1-9](?:|[0-9]{10})$|^[0-9]{20}[1-9][0-9]{4}$|^[0-9]{21}[1-9][0-9]{3}$|^[0-9]{22}[1-9][0-9]{2}$|^[0-9]{23}[1-9][0-9]$|^[0-9]{24}[1-9]$', 'gm') const str = `0 1 11 111 0100 0000 00000000000000000000 01001010100110010010 0000000000000000000000000 0100101010011010201301122`; // 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