Regular Expressions 101

Definition Group(?(DEFINE) # Note that everything is atomic, JSON does not need backtracking if it's valid # and this prevents catastrophic backtracking (?<json>(?>\s*(?&object)\s*|\s*(?&array)\s*)) (?<object>(?>\{\s*(?>(?&pair)(?>\s*,\s*(?&pair))*)?\s*\})) (?<pair>(?>(?&STRING)\s*:\s*(?&value))) (?<array>(?>\[\s*(?>(?&value)(?>\s*,\s*(?&value))*)?\s*\])) (?<value>(?>true|false|null|(?&STRING)|(?&NUMBER)|(?&object)|(?&array))) (?<STRING>(?>"(?>\\(?>["\\\/bfnrt]|u[a-fA-F0-9]{4})|[^"\\\0-\x1F\x7F]+)*")) (?<NUMBER>(?>-?(?>0|[1-9][0-9]*)(?>\.[0-9]+)?(?>[eE][+-]?[0-9]+)?)) )

Comment: Note that everything is atomic, JSON does not need backtracking if it's valid

Comment: and this prevents catastrophic backtracking

Group json(?<json>(?>\s*(?&object)\s*|\s*(?&array)\s*))

Atomic Group(?>\s*(?&object)\s*|\s*(?&array)\s*)

1st Alternative\s*(?&object)\s*

\s*any whitespace character, repeated any number of times

(?&object)calls group object as a subroutine

\s*any whitespace character, repeated any number of times

2nd Alternative\s*(?&array)\s*

\s*any whitespace character, repeated any number of times

(?&array)calls group array as a subroutine

\s*any whitespace character, repeated any number of times

Group object(?<object>(?>\{\s*(?>(?&pair)(?>\s*,\s*(?&pair))*)?\s*\}))

Atomic Group(?>\{\s*(?>(?&pair)(?>\s*,\s*(?&pair))*)?\s*\})

\{the literal { (123₁₀ / 173₈ / 7B₁₆)

\s*any whitespace character, repeated any number of times

Atomic Group(?>(?&pair)(?>\s*,\s*(?&pair))*)?

?repeats the group contents below at most once:

(?&pair)calls group pair as a subroutine

Atomic Group(?>\s*,\s*(?&pair))*

*repeats the group contents below any number of times:

\s*any whitespace character, repeated any number of times

,the literal , (44₁₀ / 54₈ / 2C₁₆)

\s*any whitespace character, repeated any number of times

(?&pair)calls group pair as a subroutine

\s*any whitespace character, repeated any number of times

\}the literal } (125₁₀ / 175₈ / 7D₁₆)

Group pair(?<pair>(?>(?&STRING)\s*:\s*(?&value)))

Atomic Group(?>(?&STRING)\s*:\s*(?&value))

(?&STRING)calls group STRING as a subroutine

\s*any whitespace character, repeated any number of times

:the literal : (58₁₀ / 72₈ / 3A₁₆)

\s*any whitespace character, repeated any number of times

(?&value)calls group value as a subroutine

Group array(?<array>(?>\[\s*(?>(?&value)(?>\s*,\s*(?&value))*)?\s*\]))

Atomic Group(?>\[\s*(?>(?&value)(?>\s*,\s*(?&value))*)?\s*\])

\[the literal [ (91₁₀ / 133₈ / 5B₁₆)

\s*any whitespace character, repeated any number of times

Atomic Group(?>(?&value)(?>\s*,\s*(?&value))*)?

?repeats the group contents below at most once:

(?&value)calls group value as a subroutine

Atomic Group(?>\s*,\s*(?&value))*

*repeats the group contents below any number of times:

\s*any whitespace character, repeated any number of times

,the literal , (44₁₀ / 54₈ / 2C₁₆)

\s*any whitespace character, repeated any number of times

(?&value)calls group value as a subroutine

\s*any whitespace character, repeated any number of times

\]the literal ] (93₁₀ / 135₈ / 5D₁₆)

Group value(?<value>(?>true|false|null|(?&STRING)|(?&NUMBER)|(?&object)|(?&array)))

Atomic Group(?>true|false|null|(?&STRING)|(?&NUMBER)|(?&object)|(?&array))

1st Alternativetrue

truethe literal text true (case sensitive)

2nd Alternativefalse

falsethe literal text false (case sensitive)

3rd Alternativenull

nullthe literal text null (case sensitive)

4th Alternative(?&STRING)

(?&STRING)calls group STRING as a subroutine

5th Alternative(?&NUMBER)

(?&NUMBER)calls group NUMBER as a subroutine

6th Alternative(?&object)

(?&object)calls group object as a subroutine

7th Alternative(?&array)

(?&array)calls group array as a subroutine

Group STRING(?<STRING>(?>"(?>\\(?>["\\\/bfnrt]|u[a-fA-F0-9]{4})|[^"\\\0-\x1F\x7F]+)*"))

Atomic Group(?>"(?>\\(?>["\\\/bfnrt]|u[a-fA-F0-9]{4})|[^"\\\0-\x1F\x7F]+)*")

Group NUMBER(?<NUMBER>(?>-?(?>0|[1-9][0-9]*)(?>\.[0-9]+)?(?>[eE][+-]?[0-9]+)?))

\Astart of string

(?&json)calls group json as a subroutine

\zend of string

Global pattern flags

x modifier: extended. Ignores unescaped whitespace and comments outside character classes

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

(?(DEFINE)
# Note that everything is atomic, JSON does not need backtracking if it's valid
# and this prevents catastrophic backtracking
(?<json>(?>\s*(?&object)\s*|\s*(?&array)\s*))
(?<object>(?>\{\s*(?>(?&pair)(?>\s*,\s*(?&pair))*)?\s*\}))
(?<pair>(?>(?&STRING)\s*:\s*(?&value)))
(?<array>(?>\[\s*(?>(?&value)(?>\s*,\s*(?&value))*)?\s*\]))
(?<value>(?>true|false|null|(?&STRING)|(?&NUMBER)|(?&object)|(?&array)))
(?<STRING>(?>"(?>\\(?>["\\\/bfnrt]|u[a-fA-F0-9]{4})|[^"\\\0-\x1F\x7F]+)*"))
(?<NUMBER>(?>-?(?>0|[1-9][0-9]*)(?>\.[0-9]+)?(?>[eE][+-]?[0-9]+)?))
)
\A(?&json)\z

New

[
    "JSON Test Pattern pass1",
    {"object with 1 member":["array with 1 element"]},
    {},
    [],
    -42,
    true,
    false,
    null,
    {
        "integer": 1234567890,
        "real": -9876.543210,
        "e": 0.123456789e-12,
        "E": 1.234567890E+34,
        "":  23456789012E66,
        "zero": 0,
        "one": 1,
        "space": " ",
        "quote": "\"",
        "backslash": "\\",
        "controls": "\b\f\n\r\t",
        "slash": "/ & \/",
        "alpha": "abcdefghijklmnopqrstuvwyz",
        "ALPHA": "ABCDEFGHIJKLMNOPQRSTUVWYZ",
        "digit": "0123456789",
        "0123456789": "digit",
        "special": "`1~!@#$%^&*()_+-={':[,]}|;.</>?",
        "hex": "\u0123\u4567\u89AB\uCDEF\uabcd\uef4A",
        "true": true,
        "false": false,
        "null": null,
        "array":[  ],
        "object":{  },
        "address": "50 St. James Street",
        "url": "http://www.JSON.org/",
        "comment": "// /* <!-- --",
        "# -- --> */": " ",
        " s p a c e d " :[1,2 , 3

,

4 , 5        ,          6           ,7        ],"compact":[1,2,3,4,5,6,7],
        "jsontext": "{\"object with 1 member\":[\"array with 1 element\"]}",
        "quotes": "&#34; \u0022 %22 0x22 034 &#x22;",
        "\/\\\"\uCAFE\uBABE\uAB98\uFCDE\ubcda\uef4A\b\f\n\r\t`1~!@#$%^&*()_+-=[]{}|;:',./<>?"
: "A key can be any string"
    },
    0.5 ,98.6
,
99.44
,

1066,
1e1,
0.1e1,
1e-1,
1e00,2e+00,2e-00
,"rosebud"]

Extraction