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

/
/
gm

Test String

Code Generator

Generated Code

const regex = /\b(\w+)\s\1\b/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('\\b(\\w+)\\s\\1\\b', 'gm') const str = `Lorem ipsum ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Mauris ultrices eros in cursus turpis massa tincidunt. Ipsum a arcu cursus vitae congue. Lobortis mattis aliquam faucibus purus in massa. Pellentesque id nibh tortor id aliquet lectus proin nibh. Ultrices tincidunt arcu arcu non sodales neque sodales ut etiam. Enim praesent elementum facilisis leo vel fringilla. Sapien eget mi proin sed. Gravida arcu ac tortor dignissim convallis aenean et tortor at. Tortor consequat id porta nibh nibh venenatis. Tincidunt augue interdum velit euismod in pellentesque massa placerat. Pretium aenean pharetra magna ac placerat vestibulum. Fermentum posuere urna urna nec tincidunt praesent semper feugiat nibh. Sagittis aliquam malesuada bibendum arcu vitae elementum curabitur. Bibendum ut tristique et egestas quis ipsum suspendisse ultrices. Consectetur purus ut faucibus pulvinar elementum integer enim. Elementum nisi quis eleifend quam adipiscing vitae proin sagittis.`; // 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