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

r"
"
gm

Test String

Code Generator

Language

Generated Code

const regex = new RegExp('(?i)(?=(((\\()?(red|gold|silver|king)( pack)?(\\))?)|((70|83|84|100|120)(s|\\'s)?)))((((\\()?(red|gold|silver|king)( pack)?(\\))? )?((70|83|84|100|120)(s|\\'s)? )?)(\\bbox\\b))', 'gm') const str = `Python does not support conditionals using lookaround, even though Python does support lookaround outside conditionals. Instead of a conditional like (?(?=regex)then|else), you can alternate two opposite lookarounds: (?=regex)then|(?!regex)else. https://www.regular-expressions.info/lookaround.html https://www.regular-expressions.info/conditional.html LOOKAHEAD to see if EITHER pattern1 or pattern2 exists pattern1 = ((\\()?(red|gold|silver|king)( pack)?(\\))?) pattern2 = ((70|83|84|100|120)(s|'s)?) IF one of the patterns exists in the string, THEN look for pattern1 box pattern2 box pattern1 pattern2 box IS NOT cases - things that I do NOT want to match box box Marlboro Box - this is a perfect example of a NOT case - I do NOT want to match this string OR maybe I do ... ARGH - NO I do not want to match BOX!! moving box - example that I NEVER want to match ... ARGHHH junk 's matchbox car matchboxracer boxer - we NEVER think about the NOT cases ... lol mitch and I fought about this for years. recently he meantioned the NEED for NOT IS cases - aka - things that I WANT TO MATCH Marlboro 100's Box Marlboro Gold Pack 100's Box Marlboro Special Blend (Gold Pack) 100's Box Marlboro Silver Pack Box Marlboro Special Blend (Red Pack) 100s Box Pall Mall RED 100 BOX Marlboro Special Blend (Gold Pack) Box `; // 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