NOTE: This plugin is included in @babel/preset-env, in ES2018

Example​

In

JavaScript

async function* agf() {
  await 1;
  yield 2;
}

Out

JavaScript

var _asyncGenerator = ...

let agf = (() => {
  var _ref = _asyncGenerator.wrap(function* () {
    yield _asyncGenerator.await(1);
    yield 2;
  });

  return function agf() {
    return _ref.apply(this, arguments);
  };
})();

For await example

JavaScript

async function f() {
  for await (let x of y) {
    g(x);
  }
}

Example Usage

JavaScript

async function* genAnswers() {
  var stream = [Promise.resolve(4), Promise.resolve(9), Promise.resolve(12)];
  var total = 0;
  for await (let val of stream) {
    total += await val;
    yield total;
  }
}

function forEach(ai, fn) {
  return ai.next().then(function(r) {
    if (!r.done) {
      fn(r);
      return forEach(ai, fn);
    }
  });
}

var output = 0;
forEach(genAnswers(), function(val) {
  output += val.value;
}).then(function() {
  console.log(output); // 42
});

Try it Out in the REPL

Installation​

• npm
• Yarn
• pnpm

pnpm add --save-dev @babel/plugin-proposal-async-generator-functions

Usage​

With a configuration file (Recommended)​

babel.config.json

{
  "plugins": ["@babel/plugin-proposal-async-generator-functions"]
}

Via CLI​

Shell

babel --plugins @babel/plugin-proposal-async-generator-functions script.js

Via Node API​

JavaScript

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

References​

• Proposal: Asynchronous iteration for ECMAScript