Are blank characters like spaces, tabs and carriage returns ignored in json strings?
For example, is {"a":"b"} equal to {"a" : "b"}?
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spaces aren't technically blank charactersFalmarri– Falmarri2010-11-11 01:18:36 +00:00Commented Nov 11, 2010 at 1:18
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34technically your brain should have parsed "blank" as "whitespace"mk12– mk122012-06-27 05:34:09 +00:00Commented Jun 27, 2012 at 5:34
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2 Answers
Yes, blanks outside a double-quoted string literal are ignored in the syntax. Specifically, the ws production in the JSON grammar in RFC 4627 shows:
Insignificant whitespace is allowed before or after any of the six structural characters. ws = *( %x20 / ; Space %x09 / ; Horizontal tab %x0A / ; Line feed or New line %x0D ; Carriage return )
7 Comments
nomen
Thanks. I had read the RFC but was unsure what kind of grammar denotation language this was -- specifically, what the * meant.
kevinarpe
* = zero or more (from regular expression notation)
aeropapa17
What about spaces embedded in numeric values: is {"a":12} equivalent to {"a":1 2} I interpret the definition "Insignificant whitespace is allowed before or after any of the six structural characters" to imply that whitespace is NOT allowed inside a numeric or date value
Greg Hewgill
@aeropapa17 That’s correct, since neither 1 nor 2 is a JSON structural character.
sengi
The grammar notation used in the spec is Augmented BNF (Backus-Naur form), which is defined in rfc-editor.org/rfc/rfc4234. There's a link to it in the JSON RFC but it's easy to miss.
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In standard JSON, whitespace outside of string literals is ignored, as has been said.
However, since your question is tagged C#, I should note that there's at least one other case in C#/.NET where whitespace in JSON does matter.
The DataContractJsonSerializer uses a special __type property to support deserializing to the correct subclass. This property is required to be the first property in an object, and to have no whitespace between the property name and the preceeding {. See this previous thread:
DataContractJsonSerializer doesn't work with formatted JSON?
At least, I have tested that the no-whitespace requirement is true as of .NET 4. Perhaps this will be changed in a future version to bring it more into line with the JSON standard?
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wprl
Danger, Will Robinson!