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

/
/
g

Test String

Code Generator

Language

Generated Code

const regex = /b\.\s(\d{4})/g; // Alternative syntax using RegExp constructor // const regex = new RegExp('b\\.\\s(\\d{4})', 'g') const str = `21 Apr 1789 - 4 Mar 1797 John Adams (b. 1735 - d. 1826) Fed 4 Mar 1797 - 4 Mar 1801 Thomas Jefferson (b. 1743 - d. 1826) D-R 4 Mar 1801 - 4 Mar 1805 Aaron Burr (b. 1756 - d. 1836) D-R 4 Mar 1805 - 20 Apr 1812 George Clinton (b. 1739 - d. 1812) D-R 4 Mar 1813 - 23 Nov 1814 Elbridge Gerry (b. 1744 - d. 1814) D-R 4 Mar 1817 - 4 Mar 1825 Daniel D. Tompkins (b. 1744 - d. 1825) D-R 4 Mar 1825 - 28 Dec 1832 John Caldwell Calhoun (b. 1782 - d. 1850) Dem 4 Mar 1833 - 4 Mar 1837 Martin van Buren (b. 1782 - d. 1862) Dem 4 Mar 1837 - 4 Mar 1841 Richard Mentor Johnson (b. 1780 - d. 1850) Dem 4 Mar 1841 - 4 Apr 1841 John Tyler (b. 1790 - d. 1862) Whg 4 Mar 1845 - 4 Mar 1849 George Mifflin Dallas (b. 1792 - d. 1864) Dem `; // 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