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JSON (JavaScript Object Notation)


JSON is a lightweight text-based format for representing structured data. It is based on a subset of JavaScript, and historically one of its main attractions was the ability to be parsed using the JavaScript eval function (although this is no longer the preferred method). There are six supported data types:

Type Example
Object { 'foo': 1, 'bar': 2 }
Array [ 1, 2, 3 ]
String "foo"
Number 2.71828
Boolean true
Null null

Objects and arrays may be nested, and may each contain a mixture of data types within them. Strings may contain any Unicode character, except that double quotes, backslashes and control characters must be escaped. JSON is usually encoded as UTF-8. Whitespace is permitted, but should typically be removed unless the JSON is intended to be human-readable.

Common uses of JSON include AJAX (as a replacement for XML), remote procedure calls using JSON-RPC, and for communicating with NoSQL databases.

Untrusted JSON expressions should not be parsed using eval because this allows for arbitrary code execution. Instead, JavaScript 1.7 and above provide explicit support for JSON by means of the JSON.parse and JSON.stringify methods. Compatibility libraries such as JSON2 or JSON3 can be used to provide an implementation of this API in environments that do not already support it. Library support is similarly available in most other programming languages.


See also

Further reading