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

Language

Generated Code

const regex = /(?:\"(?:(?<=\"(?=[^\n]))[^\n]+?(?=(?<!\\))(?=\"))?\")|(\B'(?:(?<='(?=[^\n]))[^\n]+?(?=(?<!\\))(?='))?')/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('(?:\\"(?:(?<=\\"(?=[^\\n]))[^\\n]+?(?=(?<!\\\\))(?=\\"))?\\")|(\\B\'(?:(?<=\'(?=[^\\n]))[^\\n]+?(?=(?<!\\\\))(?=\'))?\')', 'gm') const str = ` 1. Valid double-quoted strings: - "Hello" - "This is a test" - "123" - "Special characters: @#\$%^&*()_+" - "Escape sequence: \\n" 2. Valid double-quoted strings with additional characters or variables: - " test aaaaa \\" " + asdf - " test " + ( "aaaaa" ) + gdf - " test \\" " + \`" aaaa " + dfg - " test ' aaaaa \\" " + dfg - "" 3. Valid double-quoted strings with special characters: - "sas''as\\"a1\\'2 ! -_?:sa" - "''" - "\\abnb\\ajhgf\\crt098& \\"'" 4. Invalid double-quoted strings: - " test " + ( "aaaaa" ) \\" saf - "\\\\ + \\* test " \\\$ \\. dsdfs - (\\" test \\" " + " aaaa " sfgd - ' test ' + aas ( "aaaaa" ) + '\\ sd - '\\\\ + \\* test ' \\\$ \\. trace - (' test ' as ' + ' aaaa ' - '""' - '"sas' - 'ads' - 'asdasd\\"asdsa' - "klkl"klkl - "asa\\'sasa\\\\" - \\'\\\\\\' - "hhhh"klkl" - 'jkjkjk'klklk' - '\\"\\\\\\"' - '' - '\\"asa\\'sasa\\\\\\"' - "sasasasa\\\\\\\\\\\\" 1. Valid single-quoted strings: - 'Hello' - 'This is a test' - '123' - 'Special characters: @#\$%^&*()_+' - 'Escape sequence: \\n' 2. Valid single-quoted strings with additional characters or variables: - ' test aaaaa \\' ' + asdf - ' test ' + ( 'aaaaa' ) + gdf - ' test \\' ' + ' aaaa' + dfg - ' test " aaaaa \\' ' + dfg - '' 3. Valid single-quoted strings with special characters: - 'sas""as\\'a1\\"2 ! -_?:sa' - '""' - '\\abnb\\ajhgf\\crt098& \\'""' 4. Invalid single-quoted strings: - ' test ' + ( 'aaaaa' ) \\' saf - '\\\\ + \\* test ' \\\$ \\. dsdfs - (\\' test \\' + ' aaaa ' sfgd - " test \\" " + " aaaa " sfgd - ' test ' + aas ( 'aaaaa' ) + '\\ sd - '\\\\ + \\* test ' \\\$ \\. trace - (' test ' as ' + ' aaaa ' - "''" - 'sas" - "ads' - 'asdasd\\'asdsa' - "klkl"klkl - "asa\\'sasa\\\\" - \\'\\\\\\' - 'hhhh"klkl\\'\\ - \\'jkjkjk"klklk' - "\\'\\\\\\'" - '' - '\\"asa\\'sasa\\\\\\"' - 'sasasasa\\\\\\\\\\\\' `; // 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