Regular Expressions 101

Save & Share

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8
  • .NET 7.0 (C#)
  • Rust
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests

Tools

Sponsors
There are currently no sponsors. Become a sponsor today!
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

/
/
mgi

Test String

Code Generator

Language

Generated Code

const regex = /^\s*(\w+)(?:\s+(V[0-9A-F]|0x[0-9A-F]+|[0-9]+|I|DELAY|SOUND))?(?:,\s+(V[0-9A-F]|0x[0-9A-F]+|[0-9]+|DELAY))?(?:,\s+([0-9]+|0x[0-9A-F]))?\s*$/mgi; // Alternative syntax using RegExp constructor // const regex = new RegExp('^\\s*(\\w+)(?:\\s+(V[0-9A-F]|0x[0-9A-F]+|[0-9]+|I|DELAY|SOUND))?(?:,\\s+(V[0-9A-F]|0x[0-9A-F]+|[0-9]+|DELAY))?(?:,\\s+([0-9]+|0x[0-9A-F]))?\\s*$', 'mgi') const str = `NOP CLEAR RETURN JUMP 0x123 CALL 0x123 IFEQ V3, 42 IFNE V5, 0x4A IFEQ V2, V4 SET VE, 42 ADD V7, 56 SET V4, V6 OR V9, V0 AND V4, V6 XOR V2, V9 ADD VF, VD DEC V8, V3 RSH V6 SUB V3, V8 LSH VB IFNE V8, V9 SET I, 0x200 JMPO 0x230 RAND V0, 68 DRAW V2, V3, 0xF IFKEY V9 IFNKEY V8 SET V8, DELAY WAIT V7 SET DELAY, VA SET SOUND, VB ADD I, V0 SPRITE VD BCD 7 DUMP VF LOAD V3`; // 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