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https://github.com/decaffeinate/decaffeinate

Goodbye CoffeeScript, hello JavaScript!
https://github.com/decaffeinate/decaffeinate

coffeescript conversion decaffeinate

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Goodbye CoffeeScript, hello JavaScript!

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# decaffeinate [![npm](https://img.shields.io/npm/v/decaffeinate.svg)](https://www.npmjs.com/package/decaffeinate) [![Join the chat at https://gitter.im/decaffeinate](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/decaffeinate/Lobby)



Goodbye CoffeeScript, hello JavaScript!



JavaScript is the future, in part thanks to CoffeeScript. Now that it has served

its purpose, it's time to move on. Convert your CoffeeScript source to modern

JavaScript with decaffeinate.



## Installation and usage



```sh

# via yarn

$ yarn global add decaffeinate

# via npm

$ npm install -g decaffeinate



$ decaffeinate input.coffee

input.coffee → input.js



# convert all files in directory and subdirectories

$ decaffeinate .

input.coffee → input.js

subfolder/input.coffee → subfolder/input.js

```



Alternatively, paste code into the online [repl] to immediately see the output.



For real-world use cases, you'll likely want to spend some time understanding

the different options and nuances of the decaffeinate tool. You'll also likely

want to run decaffeinate using the [bulk-decaffeinate] wrapper tool, or write

your own wrapper script. See the [Conversion Guide][conversion-guide] for more

information and advice on running decaffeinate on real-world code, and see

[Cleanup suggestions after running decaffeinate][suggestions] for advice on

cleaning up the converted JavaScript code and other things to keep in mind.



## Questions and support



Feel free to join the [gitter chat room](https://gitter.im/decaffeinate/Lobby)

to ask questions, or you can file an issue on the [issues] page:



- [report a crash][crash-issue]

- [report incorrect output][wrong-issue]

- [request a feature][feature-issue]



## Status



**Complete.** The project is stable enough for production use, and has been used

to convert hundreds of thousands (probably millions) of lines of production

code. The conversion process has been extensively tested and there are few or no

known correctness bugs, although no guarantees are made.



Here are some popular open source CoffeeScript projects and their current status

when run through decaffeinate. Each project has a decaffeinate-specific fork

that is re-created from the original repo once per day.



| Project                                                   | Lines of CoffeeScript |         Conversion status          |         Test status          |

| --------------------------------------------------------- | :-------------------: | :--------------------------------: | :--------------------------: |

| [chroma.js]                                               |         3.3K          |   ![chromajs-conversion-status]    |   ![chromajs-test-status]    |

| [hubot][hubot] [\[1\]](#converted-note)                   |         3.7K          |     ![hubot-conversion-status]     |     ![hubot-test-status]     |

| [autoprefixer][autoprefixer] [\[1\]](#converted-note)     |         4.8K          | ![autoprefixer-conversion-status]  | ![autoprefixer-test-status]  |

| [coffeelint]                                              |         8.8K          |  ![coffeelint-conversion-status]   |  ![coffeelint-test-status]   |

| [vimium][vimium] [\[2\]](#correctness-note)               |          11K          |    ![vimium-conversion-status]     |    ![vimium-test-status]     |

| [coffeescript][coffeescript] [\[2\]](#correctness-note)   |          17K          | ![coffeescript-conversion-status]  | ![coffeescript-test-status]  |

| [coffeescript2][coffeescript2] [\[2\]](#correctness-note) |          17K          | ![coffeescript2-conversion-status] | ![coffeescript2-test-status] |

| [atom][atom] [\[1\]](#converted-note)                     |          51K          |     ![atom-conversion-status]      |     ![atom-test-status]      |

| [atom-org]                                                |         170K          |   ![atom-org-conversion-status]    |   ![atom-org-test-status]    |

| [codecombat]                                              |         230K          |  ![codecombat-conversion-status]   |  ![codecombat-test-status]   |



**Project builder status:** [![Build Status](https://travis-ci.org/decaffeinate/decaffeinate-example-builder.svg?branch=master)](https://travis-ci.org/decaffeinate/decaffeinate-example-builder)



**Notes:**



1. Hubot and Autoprefixer have fully moved to

   JavaScript using decaffeinate. This build runs on the last commit before the

   switch to JS. Atom has mostly moved to JavaScript using decaffeinate, so this

   build runs on an earlier revision that was primarily CoffeeScript.

2. Some CoffeeScript tests are disabled because

   they are difficult to fix and test situations that do not seem to come up in

   real-world code. The Vimium test suite has also been modified slightly to

   work around a correctness issue. See

   [How decaffeinate approaches correctness][correctness-issues] for full details.



To contribute to this list, send a pull request to the [decaffeinate-examples]

project.



In addition, decaffeinate has been used on private codebases within various

companies, such as Square, Benchling, Bugsnag, and DataFox.



Some blog posts on using decaffeinate:



- [From 200K lines of CoffeeScript to zero: making decaffeinate super-stable][benchling-blog-post]

- [Converting a large React Codebase from Coffeescript to ES6][bugsnag-blog-post]

- [Decaffeinating a Large CoffeeScript Codebase Without Losing Sleep][datafox-blog-post]

- [The Great CoffeeScript to Typescript Migration of 2017][dropbox-blog-post]



If you run into crashes or correctness issues, or you have suggestions on how

decaffeinate could be improved, feel free to file an issue on the [issues] page.



[chroma.js]: https://github.com/decaffeinate-examples/chroma.js

[hubot]: https://github.com/decaffeinate-examples/hubot

[autoprefixer]: https://github.com/decaffeinate-examples/autoprefixer

[coffeelint]: https://github.com/decaffeinate-examples/coffeelint

[vimium]: https://github.com/decaffeinate-examples/vimium

[coffeescript]: https://github.com/decaffeinate-examples/coffeescript

[coffeescript2]: https://github.com/decaffeinate-examples/coffeescript2

[atom]: https://github.com/decaffeinate-examples/atom

[atom-org]: https://github.com/decaffeinate-examples/atom-org

[codecombat]: https://github.com/decaffeinate-examples/codecombat

[decaffeinate-examples]: https://github.com/decaffeinate/decaffeinate-examples

[chromajs-conversion-status]: https://decaffeinate-examples.github.io/chroma.js/conversion-status.svg

[chromajs-test-status]: https://decaffeinate-examples.github.io/chroma.js/test-status.svg

[hubot-conversion-status]: https://decaffeinate-examples.github.io/hubot/conversion-status.svg

[hubot-test-status]: https://decaffeinate-examples.github.io/hubot/test-status.svg

[autoprefixer-conversion-status]: https://decaffeinate-examples.github.io/autoprefixer/conversion-status.svg

[autoprefixer-test-status]: https://decaffeinate-examples.github.io/autoprefixer/test-status.svg

[coffeelint-conversion-status]: https://decaffeinate-examples.github.io/coffeelint/conversion-status.svg

[coffeelint-test-status]: https://decaffeinate-examples.github.io/coffeelint/test-status.svg

[vimium-conversion-status]: https://decaffeinate-examples.github.io/vimium/conversion-status.svg

[vimium-test-status]: https://decaffeinate-examples.github.io/vimium/test-status.svg

[coffeescript-conversion-status]: https://decaffeinate-examples.github.io/coffeescript/conversion-status.svg

[coffeescript-test-status]: https://decaffeinate-examples.github.io/coffeescript/test-status.svg

[coffeescript2-conversion-status]: https://decaffeinate-examples.github.io/coffeescript2/conversion-status.svg

[coffeescript2-test-status]: https://decaffeinate-examples.github.io/coffeescript2/test-status.svg

[atom-conversion-status]: https://decaffeinate-examples.github.io/atom/conversion-status.svg

[atom-test-status]: https://decaffeinate-examples.github.io/atom/test-status.svg

[atom-org-conversion-status]: https://decaffeinate-examples.github.io/atom-org/conversion-status.svg

[atom-org-test-status]: https://decaffeinate-examples.github.io/atom-org/test-status.svg

[codecombat-conversion-status]: https://decaffeinate-examples.github.io/codecombat/conversion-status.svg

[codecombat-test-status]: https://decaffeinate-examples.github.io/codecombat/test-status.svg

[benchling-blog-post]: https://benchling.engineering/from-200k-lines-of-coffeescript-to-zero-making-decaffeinate-super-stable-4de0ca68d9bc

[bugsnag-blog-post]: https://blog.bugsnag.com/converting-a-large-react-codebase-from-coffeescript-to-es6/

[datafox-blog-post]: https://eng.datafox.com/javascript/2017/07/18/decaffeinating-large-coffeescript-codebase/

[dropbox-blog-post]: https://dropbox.tech/frontend/the-great-coffeescript-to-typescript-migration-of-2017



## Goals



- Fully automated conversion of the CoffeeScript language to modern JavaScript.

- Preserve whitespace, formatting, and comments as much as possible to allow

  a full one-time conversion of your CoffeeScript source code.

- Focus on correctness as the first priority, with some options to generate

  nicer code at the expense of 100% correctness.

- Provide helpful error messages when it encounters an unsupported language

  construct.



## Common options



- `--use-cs2`: Treat the input as CoffeeScript 2 code. CoffeeScript 2 has some

  small breaking changes and differences in behavior compared with CS1, so

  decaffeinate assumes CS1 by default and allows CS2 via this flag.

- `--use-js-modules`: Convert `require` and `module.exports` to `import` and

  `export`. Note that this may result in incorrect import statements because

  decaffeinate does not know the export style used by the other file. To

  generate correct imports, use [bulk-decaffeinate][bulk-decaffeinate] and

  enable the `useJSModules` option.



## Other options



- `--modernize-js`: Treat the input as JavaScript and only run the

  JavaScript-to-JavaScript transforms, modifying the file(s) in-place.

- `--literate`: Treat the input file as Literate CoffeeScript.

- `--disable-suggestion-comment`: Do not include a comment with followup

  suggestions at the top of the output file.

- `--no-array-includes`: Do not use `Array.prototype.includes` in generated

  code.

- `--safe-import-function-identifiers`: Comma-separated list of function names

  that may safely be in the `import`/`require` section of the file. All other

  function calls will disqualify later `require`s from being converted to

  `import`s.

- `--prefer-let`: Use `let` instead of `const` for most variables in output

  code.

- `--loose`: Enable all `--loose...` options.

- `--loose-default-params`: Convert CS default params to JS default params.

- `--loose-for-expressions`: Do not wrap expression loop targets in `Array.from`.

- `--loose-for-of`: Do not wrap JS `for...of` loop targets in `Array.from`.

- `--loose-includes`: Do not wrap in `Array.from` when converting `in` to `includes`.

- `--loose-comparison-negation`: Allow unsafe simplifications like `!(a > b)` to `a <= b`.

- `--loose-js-modules`: Allow named exports when converting to JS modules.

- `--disallow-invalid-constructors`: Give an error when constructors use `this`

  before `super` or omit the `super` call in a subclass.

- `--optional-chaining`: Target JavaScript optional chaining. Note the semantics may not match exactly.

- `--nullish-coalescing`: Target JavaScript [nullish coalescing](https://github.com/tc39/proposal-nullish-coalescing). Note the semantics may not match exactly.

- `--logical-assignment`: Use the ES2021 [logical

  assignment](https://github.com/tc39/proposal-logical-assignment) operators

  `&&=`, `||=`, and `??=`.



For more usage details, see the output of `decaffeinate --help`.



[repl]: http://decaffeinate-project.org/repl/

[bulk-decaffeinate]: https://github.com/decaffeinate/bulk-decaffeinate

[issues]: https://github.com/decaffeinate/decaffeinate/issues

[crash-issue]: https://github.com/decaffeinate/decaffeinate/issues/new?template=crash.md

[wrong-issue]: https://github.com/decaffeinate/decaffeinate/issues/new?template=wrong.md

[feature-issue]: https://github.com/decaffeinate/decaffeinate/issues/new?template=feature.md

[conversion-guide]: https://github.com/decaffeinate/decaffeinate/blob/main/docs/conversion-guide.md

[suggestions]: https://github.com/decaffeinate/decaffeinate/blob/main/docs/suggestions.md

[correctness-issues]: https://github.com/decaffeinate/decaffeinate/blob/main/docs/correctness-issues.md