Regular Expressions 101

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Function

  • Match
  • Substitution
  • List
  • Unit Tests (7)

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An explanation of your regex will be automatically generated as you type.
  • 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
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • 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

/
/
gmi

Unit Tests

given the string Y6116641N assert that regex does match
given the string 60855855V assert that regex does match
given the string 46099435Y assert that regex does match
given the string P6979540I assert that regex does match
given the string Y9330418E assert that regex does match
given the string Z3328473X assert that regex does match
given the string Z1718977P assert that regex does match

Code Generator

Language

Generated Code

const regex = /(X(-|\.)?0?\d{7}(-|\.)?[A-Z]|[A-Z](-|\.)?\d{7}(-|\.)?[0-9A-Z]|\d{8}(-|\.)?[A-Z])$/gmi; // Alternative syntax using RegExp constructor // const regex = new RegExp('(X(-|\\.)?0?\\d{7}(-|\\.)?[A-Z]|[A-Z](-|\\.)?\\d{7}(-|\\.)?[0-9A-Z]|\\d{8}(-|\\.)?[A-Z])$', 'gmi') const str = ``; 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