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

/
/
i

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

const regex = /(<head\b[^<>]*>)([\s\S]*?)(<\/head>)/i; // Alternative syntax using RegExp constructor // const regex = new RegExp('(<head\\b[^<>]*>)([\\s\\S]*?)(<\\\/head>)', 'i') const str = `<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>E-Library - Information At Your Fingertips: Printer Friendly</title> <style>body { margin: 5px 50px 40px 50px; color: #000000; font-family:Verdana, Arial, Helvetica, sans-serif; font-size: 90%; line-height: 20px; } </style> </head> <BR><BR> <CENTER> <H2>SECOND DIVISION</H2> <H2 style='background-color:#cccccc;padding-top:10px;padding-bottom:10px;'>[ G.R. No. 180416, June 02, 2014 ]</H2> <H3>ADERITO Z. YUJUICO AND BONIFACIO C. SUMBILLA, PETITIONERS, VS. CEZAR T. QUIAMBAO AND ERIC C. PILAPIL, RESPONDENTS.<BR><BR>D E C I S I O N</H3> </CENTER> <p><STRONG>PEREZ, J.:</STRONG></p> <p><div align="JUSTIFY">This case is a Petition for Review on <i>Certiorari</i><sup style="color: rgb(255, 0, 0);">[1]</sup> from the <i>Order</i><sup style="color: rgb(255, 0, 0);">[2]</sup> dated 4 June 2007 and 5 November 2007 of the Regional Trial Court (RTC), Branch 154, of Pasig City in S.C.A. No. 3047.<br><br>The facts:<br><br><center><i><u>Backgrou </html>`; const subst = `$1foo$3`; // 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