Regular Expressions 101

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  • Substitution
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  • Unit Tests (6)

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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

r"
"
g

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

const regex = new RegExp('(\\n|;|^)"([^";\\n]*?)"([^";\\n]+?)"([^";\\n]*?)"(\\n|;|$)', 'g') const str = `A stable and simple RegEx, which escapes double-quotes (") in a CSV file. ## Tests ## "Great thing?!*";"I love RegEx!";"And especially "regex101.com"!";"Just amazing..." "Something090324*?!*";"Somethi"ng090"324*?!*";"Something090324*?!*";"Something090324*?!*" Ignore"THIS"ItIsNotARealQuote?!*;"This"is"real!";HereIsNoQuoteSymbolAtAll;This"IsOnlyOneQuoteSymbol CSV: Escape double-quotes (") in quoted ## Issues ## - Does not support embedded line breaks, but you can easily modify it to support them. Note that they are currently forbitten to be more stable. - Does only allow " for quoting. (Replace it in the whole RegEx to change this) - Only works with ; as a separator. (Replace it in the whole RegEx to change this) - Does not allow separator character inside of quotes string. Look at the following example: "Example "string"";"works" "Example "string";";"fails" - Get's problems when the issue happens "too often", which means it shows up in cells which are directly side-by-side. You may work around this issue by running it multiple times: "run 1 time ";"a string with a "small" issue";"and "another" one" "run 2 times";"a string with a ""small"" issue";"and "another" one" - It only works with quoted strings (no single " are escaped; only double ones) ## Changelog ## v1.0 - 2016-01-25 - released Author: rugk <rugk@posteo.de>`; const subst = `\1"\2""\3""\4"\5`; // 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