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 = /T\s?=\s?-?\d+\.\d+\s?to\s?\d+\.\d+\s?K/g; // Alternative syntax using RegExp constructor // const regex = new RegExp('T\\s?=\\s?-?\\d+\\.\\d+\\s?to\\s?\\d+\\.\\d+\\s?K', 'g') const str = `Table 1. Coefficients for the polynomial expansion equations. Standard deviations (see introduction): σ = 5.5832 x 10-1 (low temperature range), σc,w = (4.8307 x 10-1 combined temperature ranges, weighted),  σc,uw = 3.4016 x 10-1 (combined temperature ranges, unweighted) T = 176.15 to 400.00 K T = 400.00 to 512.64 K Coefficient ρ = A + BT + CT 2 + DT 3 + … ρ = [1 + 1.75(1 - T/Tc)1/3 + 0.75(1 - T/Tc)] [ρc + A(Tc -T ) + B(Tc - T )2 + C(Tc - T )3 + D(Tc - T )4]`; // 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