@babel/plugin-transform-async-to-generator

What is @babel/plugin-transform-async-to-generator?

The @babel/plugin-transform-async-to-generator package is a Babel plugin that transforms async functions into generator functions using the regenerator runtime, which is a part of the Facebook Regenerator project. This transformation allows async functions to be used in environments that do not natively support async/await syntax by converting them into ES2015/ES6 compatible code.

What are @babel/plugin-transform-async-to-generator's main functionalities?

Transform async functions to generators

This feature allows developers to write asynchronous code using the modern async/await syntax and have it transformed into generator functions that are compatible with older JavaScript engines.

async function foo() {
  await bar();
}
// Transforms to:
function foo() {
  return regeneratorRuntime.async(function foo$(_context) {
    while (1) {
      switch (_context.prev = _context.next) {
        case 0:
          _context.next = 2;
          return regeneratorRuntime.awrap(bar());
        case 2:
        case "end":
          return _context.stop();
      }
    }
  }, null, this);
}

Other packages similar to @babel/plugin-transform-async-to-generator

babel-plugin-transform-async-to-module-method

This package is similar to @babel/plugin-transform-async-to-generator in that it transforms async functions, but it does so by delegating to a specified module method, allowing for custom handling of async functions.

fast-async

Fast-async is a Babel plugin that uses nodent to transform async/await functions. It is designed to be faster than the regenerator-based approach used by @babel/plugin-transform-async-to-generator and does not require a runtime.

babel-preset-env

While not a direct alternative, babel-preset-env includes the capability to transform async functions when the target environments specified do not support them natively. It uses @babel/plugin-transform-async-to-generator as part of its transformation suite when necessary.

README

@babel/plugin-transform-async-to-generator

Turn async functions into ES2015 generators

In Babel 7, transform-async-to-module-method was merged into this plugin

Example

In

async function foo() {
  await bar();
}

Out

var _asyncToGenerator = function (fn) {
  ...
};
var foo = _asyncToGenerator(function* () {
  yield bar();
});

Out with options

Turn async functions into a Bluebird coroutine

var Bluebird = require("bluebird");

var foo = Bluebird.coroutine(function* () {
  yield bar();
});

Installation

npm install --save-dev @babel/plugin-transform-async-to-generator

Usage

Via .babelrc (Recommended)

.babelrc

Without options:

{
  "plugins": ["@babel/plugin-transform-async-to-generator"]
}

With options:

{
  "plugins": [
    ["@babel/plugin-transform-async-to-generator", {
      "module": "bluebird",
      "method": "coroutine"
    }]
  ]
}

Via CLI

babel --plugins @babel/plugin-transform-async-to-generator script.js

Via Node API

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

References

• Proposal: Async Functions for ECMAScript