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 = /((\d*[1-9]\d*)[0](\d*[1-9]\d*)|(\d*[2-9]\d*)[1](\d*[2-9]\d*)|(\d*[3-9]\d*)[2](\d*[3-9]\d*)|(\d*[4-9]\d*)[3](\d*[4-9]\d*)|(\d*[5-9]\d*)[4](\d*[5-9]\d*)|(\d*[6-9]\d*)[5](\d*[6-9]\d*)|(\d*[7-9]\d*)[6](\d*[7-9]\d*)|(\d*[8-9]\d*)[7](\d*[8-9]\d*)|(\d*[9]\d*)[8](\d*[9]\d*))|((\d*[0-8]\d*)[9](\d*[0-8]\d*)|(\d*[0-7]\d*)[8](\d*[0-7]\d*)|(\d*[0-6]\d*)[7](\d*[0-6]\d*)|(\d*[0-5]\d*)[6](\d*[0-5]\d*)|(\d*[0-4]\d*)[5](\d*[0-4]\d*)|(\d*[0-3]\d*)[4](\d*[0-3]\d*)|(\d*[0-2]\d*)[3](\d*[0-2]\d*)|(\d*[0-1]\d*)[2](\d*[0-1]\d*)|(\d*[0]\d*)[1](\d*[0]\d*))/g; // Alternative syntax using RegExp constructor // const regex = new RegExp('((\\d*[1-9]\\d*)[0](\\d*[1-9]\\d*)|(\\d*[2-9]\\d*)[1](\\d*[2-9]\\d*)|(\\d*[3-9]\\d*)[2](\\d*[3-9]\\d*)|(\\d*[4-9]\\d*)[3](\\d*[4-9]\\d*)|(\\d*[5-9]\\d*)[4](\\d*[5-9]\\d*)|(\\d*[6-9]\\d*)[5](\\d*[6-9]\\d*)|(\\d*[7-9]\\d*)[6](\\d*[7-9]\\d*)|(\\d*[8-9]\\d*)[7](\\d*[8-9]\\d*)|(\\d*[9]\\d*)[8](\\d*[9]\\d*))|((\\d*[0-8]\\d*)[9](\\d*[0-8]\\d*)|(\\d*[0-7]\\d*)[8](\\d*[0-7]\\d*)|(\\d*[0-6]\\d*)[7](\\d*[0-6]\\d*)|(\\d*[0-5]\\d*)[6](\\d*[0-5]\\d*)|(\\d*[0-4]\\d*)[5](\\d*[0-4]\\d*)|(\\d*[0-3]\\d*)[4](\\d*[0-3]\\d*)|(\\d*[0-2]\\d*)[3](\\d*[0-2]\\d*)|(\\d*[0-1]\\d*)[2](\\d*[0-1]\\d*)|(\\d*[0]\\d*)[1](\\d*[0]\\d*))', 'g') const str = `123 234567 0123456789 87654 321 985 346 320 12342 7655338 9876789 2000000001`; // 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