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 = /^([A-Z](([A-Z]{1,2}[a-z0-9]+)+([A-Z]{1,3}[a-z0-9]+)*[A-Z]{0,3}|([a-z0-9]+[A-Z]{0,3})*|[A-Z]{1,2}))$|^([a-z][a-z0-9]*(([A-Z]{1,3}[a-z0-9]+)*[A-Z]{0,3}|([a-z0-9]+[A-Z]{1,3})*|[A-Z]{1,3}))$/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^([A-Z](([A-Z]{1,2}[a-z0-9]+)+([A-Z]{1,3}[a-z0-9]+)*[A-Z]{0,3}|([a-z0-9]+[A-Z]{0,3})*|[A-Z]{1,2}))$|^([a-z][a-z0-9]*(([A-Z]{1,3}[a-z0-9]+)*[A-Z]{0,3}|([a-z0-9]+[A-Z]{1,3})*|[A-Z]{1,3}))$', 'gm') const str = `ABCD ABCDE MdeADFAFdsADFads DeviceSNSD AabcABCD ABabcABCD ABabcABCDabcABCD ABCabcABCD ABCabcABCDabcABCDabcABCDabcABCD ABCDabcABCD ABCDabcABCDabcABCDabcABCDabcABCD HTMLParser ContextHTMLParser ABCDabcABC ABCDabcAB ABCDabcA CamelCa_1 HELLO snake_case 2PascalCase streamIOIO gREATERDtha modeADFAFdsADFads camelCa_1 contextHTMLParser hELLO AabcABCDabcABC AabcABCDabcABCD AabcABCabcABCD ABabcABCDabcABC ABabcABCDabcABCD ABabcABCabcABCD aBabcABCDabcABC aBabcABCDabcABCD aBabcABCabcABCD ababcABCDabcABC ababcABCDabcABCD ababcABCabcABCD SerialNO serialNo context camelCasE aGa alphabet serialNO modeADFdsADFads streamIO aBCabcABCabcA aBCabcA aabc123 aabcABC ab abc abcd abcde deviceSNS pathASNs dscpCP awsVPC deviceID camelCasecamelCasecamelCasecamelCasecamelCasecamelCase gREA1 gREAt gREAtREAt cP3 a1 aABC a123 modeADFsADFads a1G aG a modeADFads camelCase lThan30DaysCount lessThan30DaysCount lessThan30DaysCountA greaterThan30LessThan60DaysCount greaterThan60LessThan90DaysCount greaterThan90DaysCount pascalCase pascal2Case pascalCaseA pascal2CaseA modeA mode2A mode2A2 mode2A2A createAMode createBMode madeEasy wonderFul andMe htmlParser h aaA camel01C camel01c01 camel01C01 camel01CC01 camel0a1c1 camel0a1C1 camel0ac1b1C1 camelC camelC1 camelCA camelCa1 ibsReleaseTestVerificationRegressionSuite ibsReleaseTestVerificationRegressioNSuite ibsReleaseTestVerificationRegressioN xmlHttpRequest newCustomerId innerStopwatch supportsIpv6OnIos youTubeImporter youtubeImporter affine3D Ag ABCabcABCabc AwsVPC AaABC PacalCasePacalCasePacalCasePacalCasePacalCasePacalCase AabcABCabcABC MoeADFdsADFads ABCabcABC ABCabcAB ABabcABC ABabcAB AabcAB ABCabcABCabcA ABCabcA Aabc123 AabcABC A AB ABC StreamIO IOStream DeviceID DeviceSNS Context PascalCase Pascal2Case PascalCaseA Pascal2CaseA ModeA Mode2A Mode2A2 Mode2A2A CreateAMode CreateBMode MadeEasy WonderFul AndMe HtmlParser H AaA Camel01C Camel01c01 Camel01C01 Camel01CC01 Camel0a1c1 Camel0a1C1 Camel0ac1b1C1 CamelC CamelC1 CamelCA CamelCa1 IbsReleaseTestVerificationRegressionSuite IbsReleaseTestVerificationRegressioNSuite IbsReleaseTestVerificationRegressioN XmlHttpRequest NewCustomerId InnerStopwatch SupportsIpv6OnIos YouTubeImporter YoutubeImporter Affine3D`; // 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