JSON

Definition

“JSON (JavaScript Object Notation) is a lightweight data-interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate. It is based on a subset of the JavaScript Programming Language, Standard ECMA-262 3rd Edition - December 1999. JSON is a text format that is completely language independent but uses conventions that are familiar to programmers of the C-family of languages, including C, C++, C#, Java, JavaScript, Perl, Python, and many others. These properties make JSON an ideal data-interchange language.” (JSON, retrieved 19:07, 15 May 2007 (MEST)).

“JSON (JavaScript Object Notation) is a lightweight computer data interchange format. It is a text-based, human-readable format for representing objects and other data structures and is mainly used to transmit such structured data over a network connection (in a process called serialization). JSON finds its main application in AJAX web application programming, as a simple alternative to using XML for asynchronously transmitting structured information between client and server.” ([1], retrieved 19:07, 15 May 2007 (MEST))

Technology

• JSON is one of the rare modern data-interchange formats that is not XML.

JSON is a subset of the object literal notation of JavaScript. Since JSON is a subset of JavaScript, it can be used in the language with no muss or fuss.

JSON supports several data types including:

• number (integer, real, or floating point)
• String (double-quoted Unicode with backslash escapement)
• boolean (true and false)
• Array (an ordered sequence of values, comma-separated and enclosed in square brackets)
• Object (collection of key/value pairs, comma-separated and enclosed in curly brackets)
• null (Rob Gravell, retr. feb 2008)

 { 
   "anInt": 5555, 
   "aFloat": 55.055, 
   "aString": "testing", 
   "aBoolean": true, 
   "anArray": [1, "2", 3.34, "dog"], 
   "anObject": { 
           "prop1": "a value", 
           "prop2": "another value", 

"prop3": -9999 }, "aNull": null

}

JSON is built on two structures (JSON website, retr. May 2007):

• A collection of name/value pairs. In various languages, this is realized as an object, record, struct, dictionary, hash table, keyed list, or associative array.
• An ordered list of values. In most languages, this is realized as an array, vector, list, or sequence.

var myJSONObject = {"bindings": [
       {"ircEvent": "PRIVMSG", "method": "newURI", "regex": "^http://.*"},
       {"ircEvent": "PRIVMSG", "method": "deleteURI", "regex": "^delete.*"},
       {"ircEvent": "PRIVMSG", "method": "randomURI", "regex": "^random.*"}
   ]
};

In this example, an object is created containing a single member "bindings", which contains an array containing three objects, each containing "ircEvent", "method", and "regex" members.

Members can be retrieved using dot or subscript operators.

 myJSONObject.bindings[0].method    // "newURI"

Links

Official

• JSON HomePage
• RFC 4627 JSON specification

Tutorials and Overviews

• JSON Wikipedia page
• An Introduction to JavaScript Object Notation (JSON) by Bob Gravelle, 2008.