babel-plugin-transform-regenerator

What is babel-plugin-transform-regenerator?

The babel-plugin-transform-regenerator npm package is used to transform ES2015+ generator functions into ES5 code. This is particularly useful for writing asynchronous code in a synchronous manner using the `yield` keyword, and for ensuring compatibility with older browsers or environments that do not support generator functions natively.

What are babel-plugin-transform-regenerator's main functionalities?

Transformation of generator functions

This feature allows developers to write generator functions using the `function*` syntax and `yield` keyword. The babel-plugin-transform-regenerator will then transform this into ES5 compatible code, enabling the use of generator functions in environments that do not support them natively.

function* gen() { yield 'Hello'; yield 'World'; }

Async/Await support

Although primarily focused on generator functions, babel-plugin-transform-regenerator also plays a crucial role in enabling the use of async/await syntax in projects that use Babel for transpilation. It transforms async functions into generator functions and then into ES5 code.

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

Other packages similar to babel-plugin-transform-regenerator

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

This package transforms async functions into generator functions, similar to how babel-plugin-transform-regenerator handles async/await syntax. However, it is specifically focused on the async/await syntax rather than on generator functions in general.

regenerator-runtime

While not a Babel plugin, regenerator-runtime is often used in conjunction with babel-plugin-transform-regenerator to provide a runtime environment for the transformed generator functions. It includes a polyfill for the regenerator runtime, which is necessary for the transpiled generator functions to work.

README

babel-plugin-transform-regenerator

Transform async/generator functions with regenerator

Example

In

function* a() {
  yield 1;
}

Out

var _marked = [a].map(regeneratorRuntime.mark);

function a() {
  return regeneratorRuntime.wrap(function a$(_context) {
    while (1) {
      switch (_context.prev = _context.next) {
        case 0:
          _context.next = 2;
          return 1;

        case 2:
        case "end":
          return _context.stop();
      }
    }
  }, _marked[0], this);
}

Installation

npm install --save-dev babel-plugin-transform-regenerator

Usage

Via .babelrc (Recommended)

Without options:

{
  "plugins": ["transform-regenerator"]
}

With options:

name	default value
asyncGenerators	true
generators	true
async	true

{
  "plugins": [
    ["transform-regenerator", {
      "asyncGenerators": false,
      "generators": false,
      "async": false
    }]
  ]
}

Via CLI

babel --plugins transform-regenerator script.js

Via Node API

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