Transpile ES2017 async/await to vanilla ES6 Promise chains: a Babel plugin
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README.md

Kneden (babel-plugin-async-to-promises)

This project is currently unmaintained. If you want to take over, feel free to fork the repo. If such a fork gets maintained or contains useful improvements, I'd be willing to merge back and give repo+npm access.

Build Status Dependency Status devDependency Status

Transpile ES7 async/await to vanilla ES6 Promise chains

WARNING: Kneden is usable, but it's also not complete yet.

Do you want an ES7 async/await transpiling Babel plugin, that:

  • produces readable code - even when generator functions are not available?
  • doesn't come with a runtime your users have to download?

Then look no further! Kneden (babel-plugin-async-to-promises) can help you.

Example

In

async function test() {
  await db.destroy();
}

Out

function test() {
  return Promise.resolve().then(function () {
    return db.destroy();
  }).then(function () {});
}

(The last .then() might seem superfluous at first, but the first function doesn't actually resolve to anything so it's necessary to make a valid translation.)

Kneden tries to translate ES7 async/await to promises in a manner similar to how a human would do so. Loops are converted to recursive functions, and your code is modified in such a way that a return won't just drop you in the next part of the promise chain, but actually does what you expect it to do.

For more examples, see the test/fixtures directory for both the input and output Kneden takes/produces.

Installation

$ npm install babel-plugin-async-to-promises

Usage

Note: Kneden only supports transpiling ES5 with the addition of async/await. If you're using other ES6 features (like arrow functions, let/const, classes, etc.), make sure you transpile them down to valid ES5 code first using the babel es2015 preset. See #19 for more information.

Via .babelrc (Recommended)

.babelrc

{
  "plugins": ["async-to-promises"]
}

Via CLI

$ babel --plugins async-to-promises script.js

Via Node API

require("babel-core").transform("code", {
  plugins: ["async-to-promises"]
});

You can also use the plug-in in Browserify using babelify, in Rollup by using it in conjunction with rollup-plugin-babel, and in Webpack using babel-loader.

Unsupported

  • Return statements aren't properly supported in switch and try/catch/finally statements yet (#13)
  • No eval(); but that's true for other Babel plugins/presets as well.

Contributing

There are a couple of ways to contribute, for example by:

  • Reporting test results with your code base
  • Fixing bugs, for a nice starting task see the ones labeled 'good first bug'.

Contributions are very welcome! Just open an issue or PR.

What's up with the name?

It's Dutch for 'to knead'/'to mold' - the program molds ES7 async/await constructs into promises. It seemed applicable. Pronounciation.

The npm package name is a more descriptive one as explained in issue #22.

License

ISC


Kneden is a project by Marten de Vries.