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3.3.3 • Public • Published

🚨 Unmaintained 🚨

JSON 3 is **deprecated** and **no longer maintained**. Please don't use it in new projects, and migrate existing projects to use the native `JSON.parse` and `JSON.stringify` instead.

Thanks to everyone who contributed patches or found it useful! ❤️


No Maintenance Intended

JSON 3 was a JSON polyfill for older JavaScript platforms.


JSON is a language-independent data interchange format based on a loose subset of the JavaScript grammar. Originally popularized by Douglas Crockford, the format was standardized in the fifth edition of the ECMAScript specification. The 5.1 edition, ratified in June 2011, incorporates several modifications to the grammar pertaining to the serialization of dates.

JSON 3 exposes two functions: stringify() for serializing a JavaScript value to JSON, and parse() for producing a JavaScript value from a JSON source string. The JSON 3 parser uses recursive descent instead of eval and regular expressions, which makes it slower on older platforms compared to JSON 2. The functions behave exactly as described in the ECMAScript spec, except for the date serialization discrepancy noted below.

The project is hosted on GitHub, along with the unit tests. It is part of the BestieJS family, a collection of best-in-class JavaScript libraries that promote cross-platform support, specification precedents, unit testing, and plenty of documentation.

Date Serialization

JSON 3 deviates from the specification in one important way: it does not define Date#toISOString() or Date#toJSON(). This preserves CommonJS compatibility and avoids polluting native prototypes. Instead, date serialization is performed internally by the stringify() implementation: if a date object does not define a custom toJSON() method, it is serialized as a simplified ISO 8601 date-time string.

Several native Date#toJSON() implementations produce date time strings that do not conform to the grammar outlined in the spec. In these environments, JSON 3 will override the native stringify() implementation. There is an issue on file to make these tests less strict.

Portions of the date serialization code are adapted from the date-shim project.


Web Browsers

<script src="//cdnjs.cloudflare.com/ajax/libs/json3/3.3.2/json3.min.js"></script>
  JSON.stringify({"Hello": 123});
  // => '{"Hello":123}'
  JSON.parse("[[1, 2, 3], 1, 2, 3, 4]", function (key, value) {
    if (typeof value == "number") {
      value = value % 2 ? "Odd" : "Even";
    return value;
  // => [["Odd", "Even", "Odd"], "Odd", "Even", "Odd", "Even"]

When used in a web browser, JSON 3 exposes an additional JSON3 object containing the noConflict() and runInContext() functions, as well as aliases to the stringify() and parse() functions.

noConflict and runInContext

  • JSON3.noConflict() restores the original value of the global JSON object and returns a reference to the JSON3 object.
  • JSON3.runInContext([context, exports]) initializes JSON 3 using the given context object (e.g., window, global, etc.), or the global object if omitted. If an exports object is specified, the stringify(), parse(), and runInContext() functions will be attached to it instead of a new object.

Asynchronous Module Loaders

JSON 3 is defined as an anonymous module for compatibility with RequireJS, curl.js, and other asynchronous module loaders.

<script src="//cdnjs.cloudflare.com/ajax/libs/require.js/2.1.10/require.js"></script>
    "paths": {
      "json3": "./path/to/json3"
  }, ["json3"], function (JSON) {
    JSON.parse("[1, 2, 3]");
    // => [1, 2, 3]

To avoid issues with third-party scripts, JSON 3 is exported to the global scope even when used with a module loader. If this behavior is undesired, JSON3.noConflict() can be used to restore the global JSON object to its original value.

Note: If you intend to use JSON3 alongside another module, please do not simply concatenate these modules together, as that would cause multiple define calls in one script, resulting in errors in AMD loaders. The r.js build optimizer can be used instead if you need a single compressed file for production.

CommonJS Environments

var JSON3 = require("./path/to/json3");
JSON3.parse("[1, 2, 3]");
// => [1, 2, 3]

JavaScript Engines

JSON.stringify({"Hello": 123, "Good-bye": 456}, ["Hello"], "\t");
// => '{\n\t"Hello": 123\n}'


JSON 3 has been tested with the following web browsers, CommonJS environments, and JavaScript engines.

Web Browsers

CommonJS Environments

JavaScript Engines

  • Mozilla Rhino 1.7R3 and higher
  • WebKit JSC
  • Google V8

Known Incompatibilities

  • Attempting to serialize the arguments object may produce inconsistent results across environments due to specification version differences. As a workaround, please convert the arguments object to an array first: JSON.stringify([].slice.call(arguments, 0)).

Required Native Methods

JSON 3 assumes that the following methods exist and function as described in the ECMAScript specification:

  • The Number, String, Array, Object, Date, SyntaxError, and TypeError constructors.
  • String.fromCharCode
  • Object#toString
  • Object#hasOwnProperty
  • Function#call
  • Math.floor
  • Number#toString
  • Date#valueOf
  • String.prototype: indexOf, charCodeAt, charAt, slice, replace.
  • Array.prototype: push, pop, join.

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