153 lines
9.1 KiB
Markdown
153 lines
9.1 KiB
Markdown
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# JSON 3 #
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[](http://travis-ci.org/bestiejs/json3)
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**JSON 3** is a modern JSON implementation compatible with a variety of JavaScript platforms, including Internet Explorer 6, Opera 7, Safari 2, and Netscape 6. The current version is **3.3.2**.
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- [Development Version](http://cdnjs.cloudflare.com/ajax/libs/json3/3.3.2/json3.js) *(43 KB; uncompressed with comments)*
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- [Production Version](http://cdnjs.cloudflare.com/ajax/libs/json3/3.3.2/json3.min.js) *(3.5 KB; compressed and `gzip`-ped)*
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Special thanks to [cdnjs](http://cdnjs.com/libraries/json3/) and [jsDelivr](http://www.jsdelivr.com/#!json3) for hosting CDN copies of JSON 3.
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[JSON](http://json.org/) is a language-independent data interchange format based on a loose subset of the JavaScript grammar. Originally popularized by [Douglas Crockford](http://www.crockford.com/), the format was standardized in the [fifth edition](http://es5.github.com/) of the ECMAScript specification. The 5.1 edition, ratified in June 2011, incorporates several modifications to the grammar pertaining to the serialization of dates.
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JSON 3 exposes two functions: `stringify()` for [serializing](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/JSON/stringify) a JavaScript value to JSON, and `parse()` for [producing](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/JSON/parse) a JavaScript value from a JSON source string. It is a **drop-in replacement** for [JSON 2](http://json.org/js). The functions behave exactly as described in the ECMAScript spec, **except** for the date serialization discrepancy noted below.
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The JSON 3 parser does **not** use `eval` or regular expressions. This provides security and performance benefits in obsolete and mobile environments, where the margin is particularly significant. The complete [benchmark suite](http://jsperf.com/json3) is available on [jsPerf](http://jsperf.com/).
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The project is [hosted on GitHub](http://git.io/json3), along with the [unit tests](http://bestiejs.github.io/json3/test/test_browser.html). It is part of the [BestieJS](https://github.com/bestiejs) family, a collection of best-in-class JavaScript libraries that promote cross-platform support, specification precedents, unit testing, and plenty of documentation.
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# Changes from JSON 2 #
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JSON 3...
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* Correctly serializes primitive wrapper objects.
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* Throws a `TypeError` when serializing cyclic structures (JSON 2 recurses until the call stack overflows).
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* Utilizes **feature tests** to detect broken or incomplete *native* JSON implementations (JSON 2 only checks for the presence of the native functions). The tests are only executed once at runtime, so there is no additional performance cost when parsing or serializing values.
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**As of v3.2.3**, JSON 3 is compatible with [Prototype](http://prototypejs.org) 1.6.1 and older.
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In contrast to JSON 2, JSON 3 **does not**...
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* Add `toJSON()` methods to the `Boolean`, `Number`, and `String` prototypes. These are not part of any standard, and are made redundant by the design of the `stringify()` implementation.
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* Add `toJSON()` or `toISOString()` methods to `Date.prototype`. See the note about date serialization below.
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## Date Serialization
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**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](http://es5.github.com/#x15.9.1.15).
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**Several native `Date#toJSON()` implementations produce date time strings that do *not* conform to the grammar outlined in the spec**. For instance, all versions of Safari 4, as well as JSON 2, fail to serialize extended years correctly. Furthermore, JSON 2 and older implementations omit the milliseconds from the date-time string (optional in ES 5, but required in 5.1). Finally, in all versions of Safari 4 and 5, serializing an invalid date will produce the string `"Invalid Date"`, rather than `null`. Because these environments exhibit other serialization bugs, however, JSON 3 will override the native `stringify()` implementation.
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Portions of the date serialization code are adapted from the [`date-shim`](https://github.com/Yaffle/date-shim) project.
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# Usage #
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## Web Browsers
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<script src="//cdnjs.cloudflare.com/ajax/libs/json3/3.3.2/json3.min.js"></script>
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<script>
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JSON.stringify({"Hello": 123});
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// => '{"Hello":123}'
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JSON.parse("[[1, 2, 3], 1, 2, 3, 4]", function (key, value) {
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if (typeof value == "number") {
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value = value % 2 ? "Odd" : "Even";
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}
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return value;
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});
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// => [["Odd", "Even", "Odd"], "Odd", "Even", "Odd", "Even"]
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</script>
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**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.
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### `noConflict` and `runInContext`
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* `JSON3.noConflict()` restores the original value of the global `JSON` object and returns a reference to the `JSON3` object.
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* `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.
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### Asynchronous Module Loaders
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JSON 3 is defined as an [anonymous module](https://github.com/amdjs/amdjs-api/wiki/AMD#define-function-) for compatibility with [RequireJS](http://requirejs.org/), [`curl.js`](https://github.com/cujojs/curl), and other asynchronous module loaders.
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<script src="//cdnjs.cloudflare.com/ajax/libs/require.js/2.1.10/require.js"></script>
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<script>
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require({
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"paths": {
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"json3": "./path/to/json3"
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}
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}, ["json3"], function (JSON) {
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JSON.parse("[1, 2, 3]");
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// => [1, 2, 3]
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});
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</script>
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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.
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## CommonJS Environments
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var JSON3 = require("./path/to/json3");
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JSON3.parse("[1, 2, 3]");
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// => [1, 2, 3]
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## JavaScript Engines
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load("path/to/json3.js");
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JSON.stringify({"Hello": 123, "Good-bye": 456}, ["Hello"], "\t");
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// => '{\n\t"Hello": 123\n}'
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# Compatibility #
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JSON 3 has been **tested** with the following web browsers, CommonJS environments, and JavaScript engines.
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## Web Browsers
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- Windows [Internet Explorer](http://www.microsoft.com/windows/internet-explorer), version 6.0 and higher
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- Mozilla [Firefox](http://www.mozilla.com/firefox), version 1.0 and higher
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- Apple [Safari](http://www.apple.com/safari), version 2.0 and higher
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- [Opera](http://www.opera.com) 7.02 and higher
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- [Mozilla](http://sillydog.org/narchive/gecko.php) 1.0, [Netscape](http://sillydog.org/narchive/) 6.2.3, and [SeaMonkey](http://www.seamonkey-project.org/) 1.0 and higher
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## CommonJS Environments
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- [Node](http://nodejs.org/) 0.2.6 and higher
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- [RingoJS](http://ringojs.org/) 0.4 and higher
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- [Narwhal](http://narwhaljs.org/) 0.3.2 and higher
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## JavaScript Engines
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- Mozilla [Rhino](http://www.mozilla.org/rhino) 1.5R5 and higher
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- WebKit [JSC](https://trac.webkit.org/wiki/JSC)
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- Google [V8](http://code.google.com/p/v8)
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## Known Incompatibilities
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* 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))`.
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## Required Native Methods
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JSON 3 assumes that the following methods exist and function as described in the ECMAScript specification:
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- The `Number`, `String`, `Array`, `Object`, `Date`, `SyntaxError`, and `TypeError` constructors.
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- `String.fromCharCode`
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- `Object#toString`
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- `Function#call`
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- `Math.floor`
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- `Number#toString`
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- `Date#valueOf`
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- `String.prototype`: `indexOf`, `charCodeAt`, `charAt`, `slice`.
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- `Array.prototype`: `push`, `pop`, `join`.
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# Contribute #
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Check out a working copy of the JSON 3 source code with [Git](http://git-scm.com/):
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$ git clone git://github.com/bestiejs/json3.git
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$ cd json3
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If you'd like to contribute a feature or bug fix, you can [fork](http://help.github.com/fork-a-repo/) JSON 3, commit your changes, and [send a pull request](http://help.github.com/send-pull-requests/). Please make sure to update the unit tests in the `test` directory as well.
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Alternatively, you can use the [GitHub issue tracker](https://github.com/bestiejs/json3/issues) to submit bug reports, feature requests, and questions, or send tweets to [@kitcambridge](http://twitter.com/kitcambridge).
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JSON 3 is released under the [MIT License](http://kit.mit-license.org/).
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