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

/
/
gi

Test String

Code Generator

Language

Generated Code

const regex = /(?P<amount>-?\d+(?:\.\d*)?)[^\S\n]*(?P<degrees>°|deg(?:rees?)?|in)?[^\S\n]*(?P<unit>c(?:(?=el[cs]ius\b|entigrades?\b|\b))|f(?:(?=ahrenheit\b|\b))|k(?:(?=elvins?\b|\b)))/gi; // Alternative syntax using RegExp constructor // const regex = new RegExp('(?P<amount>-?\\d+(?:\\.\\d*)?)[^\\S\\n]*(?P<degrees>°|deg(?:rees?)?|in)?[^\\S\\n]*(?P<unit>c(?:(?=el[cs]ius\\b|entigrades?\\b|\\b))|f(?:(?=ahrenheit\\b|\\b))|k(?:(?=elvins?\\b|\\b)))', 'gi') const str = `70 degrees celsius 70 degree fahrenheit 70 degrees c 70 degrees f 70 ° f 70 ° c 70°c 70°f 70 deg celsius 70 deg centigrade 70 deg fahrenheit -30.5 in Kelvin -30.5 degrees Kelvin -30.5 Kelvin 70F 70C 70 c 70 f 70k 100 deg celcius Oh, it seems I have an oven from Europe. If the recipe calls for 325 degrees fahrenheit and water boils at 100 centigrades, then... multiply, and... voila! Set your oven for 650 degrees celsius--that should make your cookies crispy-brown! # Failures 70 degrees # too ambiguous 70 deg felsius # ensure we don't mix fahrenheit and celsius `; // 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