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

/
/
gx

Test String

Code Generator

Generated Code

const regex = /(?&object) # Find the object #################### (?(DEFINE) (?<name> " \s* [^\s"]+ \s* " ) (?<value> (?> (?: (?&string) | (?&number) | (?&object) | (?&array) | (?&T_F_N) ) ) ) (?<string> " [^"]* " ) (?<number> \d+ ) (?<array> \[ (?: \s* (?&value) (?> (?: \s* , \s* (?&value) )* ) )? \s* \] ) (?<T_F_N> true | false | null ) (?<object> { (?: \s* (?&name) \s* : \s* (?&value) (?: \s* , \s* (?&name) \s* : \s* (?&value) )* \s* ) } ) ) /g; // Alternative syntax using RegExp constructor // const regex = new RegExp('(?&object) # Find the object #################### (?(DEFINE) (?<name> " \\s* [^\\s"]+ \\s* " ) (?<value> (?> (?: (?&string) | (?&number) | (?&object) | (?&array) | (?&T_F_N) ) ) ) (?<string> " [^"]* " ) (?<number> \\d+ ) (?<array> \\[ (?: \\s* (?&value) (?> (?: \\s* , \\s* (?&value) )* ) )? \\s* \\] ) (?<T_F_N> true | false | null ) (?<object> { (?: \\s* (?&name) \\s* : \\s* (?&value) (?: \\s* , \\s* (?&name) \\s* : \\s* (?&value) )* \\s* ) } ) ) ', 'g') const str = `{ "firstName": "Duke", "lastName": "Java", "age": 18, "streetAddress": "100 Internet Dr", "city": "JavaTown", "state": "JA", "postalCode": "12345", "phoneNumbers": [ { "Mobile": "111-111-1111" }, { "Home": "222-222-2222" } ] }`; // 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