Babel 6 regeneratorRuntime is not defined

Question

I'm trying to use async, await from scratch on Babel 6, but I'm getting regeneratorRuntime is not defined.

.babelrc file

{
    "presets": [ "es2015", "stage-0" ]
}

package.json file

"devDependencies": {
    "babel-core": "^6.0.20",
    "babel-preset-es2015": "^6.0.15",
    "babel-preset-stage-0": "^6.0.15"
}

.js file

"use strict";
async function foo() {
  await bar();
}
function bar() { }
exports.default = foo;

Using it normally without the async/await works just fine. Any ideas what I'm doing wrong?

Answer 1

Alternatively, if you don't need all the modules babel-polyfill provides, you can just specify babel-regenerator-runtime in your webpack config:

module.exports = {
  entry: ['babel-regenerator-runtime', './test.js'],

  // ...
};

When using webpack-dev-server with HMR, doing this reduced the number of files it has to compile on every build by quite a lot. This module is installed as part of babel-polyfill so if you already have that you're fine, otherwise you can install it separately with npm i -D babel-regenerator-runtime.

Answer 2

Update your .babelrc file according to the following examples, it will work.

If you are using @babel/preset-env package

{
  "presets": [
    [
      "@babel/preset-env", {
        "targets": {
          "node": "current"
        }
      }
    ]
  ]
}
or if you are using babel-preset-env package

{
  "presets": [
    [
      "env", {
        "targets": {
          "node": "current"
        }
      }
    ]
  ]
}

Answer 3

My simple solution:

npm install --save-dev babel-plugin-transform-runtime
npm install --save-dev babel-plugin-transform-async-to-generator

.babelrc

{
  "presets": [
    ["latest", {
      "es2015": {
        "loose": true
      }
    }],
    "react",
    "stage-0"
  ],
  "plugins": [
    "transform-runtime",
    "transform-async-to-generator"
  ]
}

Answer 4

I had a setup
with webpack using presets: ['es2015', 'stage-0']
and mocha that was running tests compiled by webpack.

To make my async/await in tests work all I had to do is add mocha --require babel-polyfill option.

Answer 5

I get this error using gulp with rollup when I tried to use ES6 generators:

gulp.task('scripts', () => {
  return rollup({
    entry: './app/scripts/main.js',
    format: "iife",
    sourceMap: true,
    plugins: [babel({
      exclude: 'node_modules/**',
      "presets": [
        [
          "es2015-rollup"
        ]
      ],
      "plugins": [
        "external-helpers"
      ]
    }),
    includePaths({
      include: {},
      paths: ['./app/scripts'],
      external: [],
      extensions: ['.js']
    })]
  })

  .pipe(source('app.js'))
  .pipe(buffer())
  .pipe(sourcemaps.init({
    loadMaps: true
  }))
  .pipe(sourcemaps.write('.'))
  .pipe(gulp.dest('.tmp/scripts'))
  .pipe(reload({ stream: true }));
});

I may case the solution was to include babel-polyfill as bower component:

bower install babel-polyfill --save

and add it as dependency in index.html:

<script src="/bower_components/babel-polyfill/browser-polyfill.js"></script>

Answer 6

i had regeneratorRuntime is not defined error when i used 'async' and 'await' in my react app 'async' and 'await' is a new keywords in ES7 for that you should use babel-preset-es2017 install this devDependencies:

`

"babel-preset-es2017": "^6.24.1",
"babel-preset-react": "^6.24.1",
"babel-preset-stage-0": "^6.24.1", `

and use this

"presets": [ "es2017" , "stage-0" , "react" ]