| 1 | **Esprima** ([esprima.org](http://esprima.org), BSD license) is a high performance,
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| 2 | standard-compliant [ECMAScript](http://www.ecma-international.org/publications/standards/Ecma-262.htm)
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| 3 | parser written in ECMAScript (also popularly known as
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| 4 | [JavaScript](http://en.wikipedia.org/wiki/JavaScript>JavaScript)).
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| 5 | Esprima is created and maintained by [Ariya Hidayat](http://twitter.com/ariyahidayat),
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| 6 | with the help of [many contributors](https://github.com/ariya/esprima/contributors).
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| 7 |
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| 8 | **Esprima-FB** is a fork of the [Harmony branch](https://github.com/ariya/esprima/tree/harmony) of Esprima that implements [JSX specification](https://github.com/facebook/jsx) on top of ECMAScript syntax.
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| 9 |
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| 10 | ### Features
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| 11 |
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| 12 | - Full support for ECMAScript 5.1 ([ECMA-262](http://www.ecma-international.org/publications/standards/Ecma-262.htm))
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| 13 | - Experimental support for ES6/Harmony (module, class, destructuring, ...)
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| 14 | - Full support for [JSX syntax extensions](https://github.com/facebook/jsx).
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| 15 | - Sensible [syntax tree format](https://github.com/facebook/jsx/blob/master/AST.md) compatible with Mozilla
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| 16 | [Parser AST](https://developer.mozilla.org/en/SpiderMonkey/Parser_API)
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| 17 | - Optional tracking of syntax node location (index-based and line-column)
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| 18 | - Heavily tested (> 650 [unit tests](http://esprima.org/test/) with [full code coverage](http://esprima.org/test/coverage.html))
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| 19 | - Ongoing support for ES6/Harmony (module, class, destructuring, ...)
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| 20 |
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| 21 | ### Versioning rules
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| 22 |
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| 23 | In order to follow semver rules and keep reference to original Esprima versions at the same time, we left 3 digits of each version part to refer to upstream harmony branch. We then take the most significant digit.
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| 24 |
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| 25 | **Example:** 4001.3001.0000-dev-harmony-fb aligns with 1.1.0-dev-harmony (aka 001.001.000-dev-harmony) in upstream, with our own changes on top.
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| 26 |
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| 27 | Esprima-FB serves as a **building block** for JSX language tools and transpiler implementations (such as [React](https://github.com/facebook/react) or [JSXDOM](https://github.com/vjeux/jsxdom)).
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| 28 |
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| 29 | Esprima-FB runs on many popular web browsers, as well as other ECMAScript platforms such as
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| 30 | [Rhino](http://www.mozilla.org/rhino) and [Node.js](https://npmjs.org/package/esprima).
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| 31 |
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| 32 | For more information on original Esprima, check the web site [esprima.org](http://esprima.org).
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