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

/
/
gu

Test String

Code Generator

Language

Generated Code

const regex = /[\t\u000b\u000c\ufeff\p{Space_Separator}\n\r\u2028\u2029]|\/\*(?:(?!\*\/)[^]*?)?\*\/|<!--(?:(?!-->)[^]*?)?-->|\/\/[^\n\r\u2028\u2029]*|#?(?:[$_\p{ID_Start}]|\\(?:u[0-9a-fA-F]{4}|u\{(?:(?:10|[0-9])[0-9a-fA-F]{4}|[0-9a-fA-F]{1,5})\}))(?:[$\p{ID_Continue}]|\\(?:u[0-9a-fA-F]{4}|u\{(?:(?:10|[0-9])[0-9a-fA-F]{4}|[0-9a-fA-F]{1,5})\}))*|(?:\?\.(?![0-9])|\{|\(|\)|\[|\]|;|,|~|:|\.\.\.|\.|<<=|<<|<=|<|>>>=|>>>|>>=|>>|>=|>|===|==|=>|=|!==|!=|!|\*\*=|\*\*|\*=|\*|%=|%|\+\+|\+=|\+|--|-=|-|&&=|&&|&=|&|\|\|=|\|\||\|=|\||\?\?=|\?\?|\?|\^=|\^)|(?:(?:0|[1-9](?:_?(?:[0-9](?:_[0-9])*)+)?|0[0-7]*[89][0-9]+)\.?(?:[0-9](?:_[0-9])*)*(?:[eE][+-]?(?:[0-9](?:_[0-9])*)+)?)|(?:\.(?:[0-9](?:_[0-9])*)+(?:[eE][+-]?(?:[0-9](?:_[0-9])*)+)?)|(?:(?:0|[1-9](?:_?(?:[0-9](?:_[0-9])*)+)?|0[0-7]*[89][0-9]+)?[eE][+-]?(?:[0-9](?:_[0-9])*)+)|(?:0|[1-9](?:_?(?:[0-9](?:_[0-9])*)+)?)n|(?:0[bB](?:[01](?:_[01])*)+|0[oO](?:[0-7](?:_[0-7])*)+|0[xX](?:[0-9a-fA-F](?:_[0-9a-fA-F])*)+)n?|0[0-7]+|(["'])(?:(?!\1)[^\\\n\r]|\\(?:['"\\bfnrtv]|[^'"\\bfnrtv0-9xu\n\r\u2028\u2029]|0(?![0-9])|0(?=[89])|[1-7](?![0-7])|[0-3][0-7]{1,2}|[4-7][0-7]|[89]|x[0-9a-fA-F]{2}|u[0-9a-fA-F]{4}|u\{(?:(?:10|[0-9])[0-9a-fA-F]{4}|[0-9a-fA-F]{1,5})\})|\\(?:\r\n|\n|\r|\u2028|\u2029))*\1|`(?:\$(?!\{)|\\(?:['"\\bfnrtv]|[^'"\\bfnrtv0-9xu\n\r\u2028\u2029]|0(?![0-9])|x[0-9a-fA-F]{2}|(?:u[0-9a-fA-F]{4}|u\{(?:(?:10|[0-9])[0-9a-fA-F]{4}|[0-9a-fA-F]{1,5})\}))|\\(?:0[0-9]|[1-9]|x(?![0-9a-fA-F])|x[0-9a-fA-F](?![0-9a-fA-F])|u(?![0-9a-fA-F{])|u[0-9a-fA-F]{1,3}(?![0-9a-fA-F])|u\{(?![0-9a-fA-F])|u\{(?:1[1-9a-fA-F][0-9a-fA-F]{4}|[2-9a-fA-F][0-9a-fA-F]{5}|[0-9a-fA-F]{7,})(?![0-9a-fA-F])|u\{(?:(?:10|[0-9])[0-9a-fA-F]{4}|[0-9a-fA-F]{1,5})(?![0-9a-fA-F}]))|\\(?:\r\n|\n|\r|\u2028|\u2029)|\r\n|[^`\\$])*(?:`|\$\{)|#![^\n\r\u2028\u2029]*|\/(?:[^\n\r\u2028\u2029*\\/[]|\\[^\n\r\u2028\u2029]|\[(?:[^\n\r\u2028\u2029\]\\]|\\[^\n\r\u2028\u2029])*\])(?:[^\n\r\u2028\u2029\\/[]|\\[^\n\r\u2028\u2029]|\[(?:[^\n\r\u2028\u2029\]\\]|\\[^\n\r\u2028\u2029])*\])*\/[$\p{ID_Continue}]*/gu; // Alternative syntax using RegExp constructor // const regex = new RegExp('[\\t\\u000b\\u000c\\ufeff\\p{Space_Separator}\\n\\r\\u2028\\u2029]|\\\/\\*(?:(?!\\*\\\/)[^]*?)?\\*\\\/|<!--(?:(?!-->)[^]*?)?-->|\\\/\\\/[^\\n\\r\\u2028\\u2029]*|#?(?:[$_\\p{ID_Start}]|\\\\(?:u[0-9a-fA-F]{4}|u\\{(?:(?:10|[0-9])[0-9a-fA-F]{4}|[0-9a-fA-F]{1,5})\\}))(?:[$\\p{ID_Continue}]|\\\\(?:u[0-9a-fA-F]{4}|u\\{(?:(?:10|[0-9])[0-9a-fA-F]{4}|[0-9a-fA-F]{1,5})\\}))*|(?:\\?\\.(?![0-9])|\\{|\\(|\\)|\\[|\\]|;|,|~|:|\\.\\.\\.|\\.|<<=|<<|<=|<|>>>=|>>>|>>=|>>|>=|>|===|==|=>|=|!==|!=|!|\\*\\*=|\\*\\*|\\*=|\\*|%=|%|\\+\\+|\\+=|\\+|--|-=|-|&&=|&&|&=|&|\\|\\|=|\\|\\||\\|=|\\||\\?\\?=|\\?\\?|\\?|\\^=|\\^)|(?:(?:0|[1-9](?:_?(?:[0-9](?:_[0-9])*)+)?|0[0-7]*[89][0-9]+)\\.?(?:[0-9](?:_[0-9])*)*(?:[eE][+-]?(?:[0-9](?:_[0-9])*)+)?)|(?:\\.(?:[0-9](?:_[0-9])*)+(?:[eE][+-]?(?:[0-9](?:_[0-9])*)+)?)|(?:(?:0|[1-9](?:_?(?:[0-9](?:_[0-9])*)+)?|0[0-7]*[89][0-9]+)?[eE][+-]?(?:[0-9](?:_[0-9])*)+)|(?:0|[1-9](?:_?(?:[0-9](?:_[0-9])*)+)?)n|(?:0[bB](?:[01](?:_[01])*)+|0[oO](?:[0-7](?:_[0-7])*)+|0[xX](?:[0-9a-fA-F](?:_[0-9a-fA-F])*)+)n?|0[0-7]+|(["\'])(?:(?!\\1)[^\\\\\\n\\r]|\\\\(?:[\'"\\\\bfnrtv]|[^\'"\\\\bfnrtv0-9xu\\n\\r\\u2028\\u2029]|0(?![0-9])|0(?=[89])|[1-7](?![0-7])|[0-3][0-7]{1,2}|[4-7][0-7]|[89]|x[0-9a-fA-F]{2}|u[0-9a-fA-F]{4}|u\\{(?:(?:10|[0-9])[0-9a-fA-F]{4}|[0-9a-fA-F]{1,5})\\})|\\\\(?:\\r\\n|\\n|\\r|\\u2028|\\u2029))*\\1|`(?:\\$(?!\\{)|\\\\(?:[\'"\\\\bfnrtv]|[^\'"\\\\bfnrtv0-9xu\\n\\r\\u2028\\u2029]|0(?![0-9])|x[0-9a-fA-F]{2}|(?:u[0-9a-fA-F]{4}|u\\{(?:(?:10|[0-9])[0-9a-fA-F]{4}|[0-9a-fA-F]{1,5})\\}))|\\\\(?:0[0-9]|[1-9]|x(?![0-9a-fA-F])|x[0-9a-fA-F](?![0-9a-fA-F])|u(?![0-9a-fA-F{])|u[0-9a-fA-F]{1,3}(?![0-9a-fA-F])|u\\{(?![0-9a-fA-F])|u\\{(?:1[1-9a-fA-F][0-9a-fA-F]{4}|[2-9a-fA-F][0-9a-fA-F]{5}|[0-9a-fA-F]{7,})(?![0-9a-fA-F])|u\\{(?:(?:10|[0-9])[0-9a-fA-F]{4}|[0-9a-fA-F]{1,5})(?![0-9a-fA-F}]))|\\\\(?:\\r\\n|\\n|\\r|\\u2028|\\u2029)|\\r\\n|[^`\\\\$])*(?:`|\\$\\{)|#![^\\n\\r\\u2028\\u2029]*|\\\/(?:[^\\n\\r\\u2028\\u2029*\\\\\/[]|\\\\[^\\n\\r\\u2028\\u2029]|\\[(?:[^\\n\\r\\u2028\\u2029\\]\\\\]|\\\\[^\\n\\r\\u2028\\u2029])*\\])(?:[^\\n\\r\\u2028\\u2029\\\\\/[]|\\\\[^\\n\\r\\u2028\\u2029]|\\[(?:[^\\n\\r\\u2028\\u2029\\]\\\\]|\\\\[^\\n\\r\\u2028\\u2029])*\\])*\\\/[$\\p{ID_Continue}]*', 'gu') const str = `const a = 5; const b = \`\${a} \${a}\`;`; // 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