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(?<!\d.)(3[47]\d{2}([ -]?)(?!(\d)\3{5}|123456|234567|345678|424242|545454)\d{6}\2(?!(\d)\4{4})\d{5}|((4\d|5[1-5]|65)\d{2}|6011)([ -]?)(?!(\d)\8{3}|4242|5454|1234|3456|5678|2345|4567)\d{4}\7(?!(\d)\9{3})\d{4}\7\d{4})(\b|\s)(?!.\d\d)/g; // Alternative syntax using RegExp constructor // const regex = new RegExp('\\b(?<!\\d.)(3[47]\\d{2}([ -]?)(?!(\\d)\\3{5}|123456|234567|345678|424242|545454)\\d{6}\\2(?!(\\d)\\4{4})\\d{5}|((4\\d|5[1-5]|65)\\d{2}|6011)([ -]?)(?!(\\d)\\8{3}|4242|5454|1234|3456|5678|2345|4567)\\d{4}\\7(?!(\\d)\\9{3})\\d{4}\\7\\d{4})(\\b|\\s)(?!.\\d\\d)', 'g') const str = `ALL strings in the first section should match some 4270446050075048 4270-4460-5007-5048 this:4270 4460 5007 5048. 4270 4460 5007 5048 4/20 4270 4460 5007 5048 what 4270 4460 5007 5048 4270 4460 5007 5048 12/20 5105105105105100 5200828282828210 --- (the following should not match - test numbers) 5454545454545454 4123456789012345 4242424242424242 42704460500750a8 4111111111111111 5111111111111111 5555555555555555 3333333333333333 3111111111111111 --- (the following should NOT match) 4270 4460 5007 5048 1234 4270 4270 4460 5007 504 42811293test123 427044605007504812345083 5095 5179 5157 5219 5187 5095 <--- FALSE POSITIVE (contains valid CC but has lots of exra digits) this:4270 4460 5007 50482 4270 4460 5007 5048 123 4270 4460 5007 5048 1234 Known False positive (test number): 5535 3545 5455 4444 `; // 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