babel-plugin-transform-async-generator-functions

babel-plugin-transform-async-generator-functions

Turn async generator functions and for-await statements to ES2015 generators

Example

In

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

Out

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

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

Example Usage

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 install --save-dev babel-plugin-transform-async-generator-functions

Usage

Via .babelrc (Recommended)

.babelrc

{
  "plugins": ["transform-async-generator-functions"]
}

Via CLI

babel --plugins transform-async-generator-functions script.js

Via Node API

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

References

• Proposal: Asynchronous iteration for ECMAScript