JSON is the ideal method for data interchange; consider its compact payload, native support in JavaScript, and its interoperability with other languages (via a bridge), and it is surprising that support for JSON is not more ubiquitous. While Yahoo and Google are now offering data feeds in JSON format, I am anxious for other information providors to follow suit.
What Is JSON
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.
Syntax
JSON is a subset of the object literal notation of JavaScript and is commonly used with that language. However the basic types and data structures of most other programming languages can also be represented in JSON, and the format can therefore be used to exchange structured data between programs written in different languages. Code for parsing and generating JSON (the latter is also known as "stringifying") is available for the following languages: ActionScript, C, C++, C#, ColdFusion, Common Lisp, Delphi/Object pascal, E, Erlang, Haskell, Io[1] Java, JavaScript, Lasso (programming language), Limbo, Lua, ML, Objective-C, Objective CAML, Perl, PHP, Python, Rebol, Ruby, Smalltalk and Tcl.
JSON is built on two structures:
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.
These are universal data structures. Virtually all modern programming languages support them in one form or another. It makes sense that a data format that is interchangable with programming languages also be based on these structures.
In JSON, they take on these forms:
An object is an unordered set of name/value pairs. An object begins with { (left brace) and ends with } (right brace). Each name is followed by : (colon) and the name/value pairs are separated by , (comma).
An array is an ordered collection of values. An array begins with [ (left bracket) and ends with ] (right bracket). Values are separated by , (comma).
A value can be a string in double quotes, or a number, or true or false or null, or an object or an array. These structures can be nested.
A string is a collection of zero or more Unicode characters, wrapped in double quotes, using backslash escapes. A character is represented as a single character string. A string is very much like a C or Java string.
A number is very much like a C or Java number, except that the octal and hexadecimal formats are not used.
Whitespace can be inserted between any pair of tokens. Excepting a few encoding details, that completely describes the language.
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