Regular Expressions 101

Save & Manage Regex

  • Current Version: 1
  • Save & Share
  • Community Library

Flavor

  • PCRE2 (PHP)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java
  • .NET 7.0 (C#)
  • Rust
  • PCRE (Legacy)
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests
Sponsors
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
Processing...

Test String

Code Generator

Language

Generated Code

const regex = /^(?: (?:0[1-9]|1\d|2[0-8])([\/-])(?:02)\1(?:\d+)| (?:0[1-9]|1\d|2\d)([\/-])(?:02)\2(?:(?:\d*?(?:(?:0[48]|[13579][26]|[2468][048])|(?:(?:[02468][048]|[13579][26])00))|[48]00|[48])(?=\D|\b))| (?:0[1-9]|1\d|2\d|30)([\/-])(?:0[469]|11)\3(?:\d+)| (?:0[1-9]|1\d|2\d|3[01])([\/-])(?:0[13578]|1[02])\4(?:\d+)| (?:02)([\/-])(?:0[1-9]|1\d|2[0-8])\5(?:\d+)| (?:02)([\/-])(?:0[1-9]|1\d|2\d)\6(?:(?:\d*?(?:(?:0[48]|[13579][26]|[2468][048])|(?:(?:[02468][048]|[13579][26])00))|[48]00|[48])(?=\D|\b))| (?:0[469]|11)([\/-])(?:0[1-9]|1\d|2\d|30)\7(?:\d+)| (?:0[13578]|1[02])([\/-])(?:0[1-9]|1\d|2\d|3[01])\8(?:\d+)| (?:\d+)([\/-])(?:0[1-9]|1\d|2[0-8])\9(?:02)| (?:(?:\d*?(?:(?:0[48]|[13579][26]|[2468][048])|(?:(?:[02468][048]|[13579][26])00))|[48]00|[48])(?=\D|\b))([\/-])(?:0[1-9]|1\d|2\d)\10(?:02)| (?:\d+)([\/-])(?:0[1-9]|1\d|2\d|30)\11(?:0[469]|11)| (?:\d+)([\/-])(?:0[1-9]|1\d|2\d|3[01])\12(?:0[13578]|1[02])| (?:\d+)([\/-])(?:02)\13(?:0[1-9]|1\d|2[0-8])| (?:(?:\d*?(?:(?:0[48]|[13579][26]|[2468][048])|(?:(?:[02468][048]|[13579][26])00))|[48]00|[48])(?=\D|\b))([\/-])(?:02)\14(?:0[1-9]|1\d|2\d)| (?:\d+)([\/-])\15(?:0[469]|11)(?:0[1-9]|1\d|2\d|30)| (?:\d+)([\/-])(?:0[13578]|1[02])\16(?:0[1-9]|1\d|2\d|3[01]) )$/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^(?: (?:0[1-9]|1\\d|2[0-8])([\\\/-])(?:02)\\1(?:\\d+)| (?:0[1-9]|1\\d|2\\d)([\\\/-])(?:02)\\2(?:(?:\\d*?(?:(?:0[48]|[13579][26]|[2468][048])|(?:(?:[02468][048]|[13579][26])00))|[48]00|[48])(?=\\D|\\b))| (?:0[1-9]|1\\d|2\\d|30)([\\\/-])(?:0[469]|11)\\3(?:\\d+)| (?:0[1-9]|1\\d|2\\d|3[01])([\\\/-])(?:0[13578]|1[02])\\4(?:\\d+)| (?:02)([\\\/-])(?:0[1-9]|1\\d|2[0-8])\\5(?:\\d+)| (?:02)([\\\/-])(?:0[1-9]|1\\d|2\\d)\\6(?:(?:\\d*?(?:(?:0[48]|[13579][26]|[2468][048])|(?:(?:[02468][048]|[13579][26])00))|[48]00|[48])(?=\\D|\\b))| (?:0[469]|11)([\\\/-])(?:0[1-9]|1\\d|2\\d|30)\\7(?:\\d+)| (?:0[13578]|1[02])([\\\/-])(?:0[1-9]|1\\d|2\\d|3[01])\\8(?:\\d+)| (?:\\d+)([\\\/-])(?:0[1-9]|1\\d|2[0-8])\\9(?:02)| (?:(?:\\d*?(?:(?:0[48]|[13579][26]|[2468][048])|(?:(?:[02468][048]|[13579][26])00))|[48]00|[48])(?=\\D|\\b))([\\\/-])(?:0[1-9]|1\\d|2\\d)\\10(?:02)| (?:\\d+)([\\\/-])(?:0[1-9]|1\\d|2\\d|30)\\11(?:0[469]|11)| (?:\\d+)([\\\/-])(?:0[1-9]|1\\d|2\\d|3[01])\\12(?:0[13578]|1[02])| (?:\\d+)([\\\/-])(?:02)\\13(?:0[1-9]|1\\d|2[0-8])| (?:(?:\\d*?(?:(?:0[48]|[13579][26]|[2468][048])|(?:(?:[02468][048]|[13579][26])00))|[48]00|[48])(?=\\D|\\b))([\\\/-])(?:02)\\14(?:0[1-9]|1\\d|2\\d)| (?:\\d+)([\\\/-])\\15(?:0[469]|11)(?:0[1-9]|1\\d|2\\d|30)| (?:\\d+)([\\\/-])(?:0[13578]|1[02])\\16(?:0[1-9]|1\\d|2\\d|3[01]) )$', 'gm') const str = `30/11/2017 30-11-2017 2017-05-31 30-/11-/2017 30-11/2017`; // 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