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

Substitution

Processing...

Code Generator

Language

Generated Code

const regex = /^((?:\S+\s+){4})/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^((?:\\S+\\s+){4})', 'gm') const str = `EE84 1484.74 1364.99 62.5 2 1 0 1 EE85 505.23 841.63 60. 2 1 0 1 EE86 945.95 913.39 100. 1 0 0 0 P3 972.44 1126.12 100. 1 0 0 0 P28 980.0 1119.0 100. 1 0 0 0 P100 964.03 1125.93 100. 1 0 0 0 P102 963.49 1133.71 100. 1 0 0 0 P106 974.06 1150.73 100. 1 0 0 0 P108 1017.36 1062.47 100. 1 0 0 0 P109 965.31 1151.14 100. 1 0 0 0 `; const subst = `${1}0 `; // The substituted value will be contained in the result variable const result = str.replace(regex, subst); console.log('Substitution result: ', result);

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