Why am I getting a \'regeneratorRuntime is not defined\' error in Babel 6, and how can I fix it?

"regeneratorRuntime is not defined" error in Babel 6

When using Babel 6, you may encounter "regeneratorRuntime is not defined" defined" error, especially when using async/await syntax. This error indicates that you are missing a required dependency or configuration when setting up Babel.

To resolve this issue, you need to install and configure babel-polyfill. The library provides a set of polyfills that can be used to support modern JavaScript features, such as async/await, in environments that do not support natively supported functionality.

Install dependencies

First, install babel-polyfill and other required Babel dependencies using npm:

npm i -D babel-core babel-polyfill babel-preset-es2015 babel-preset-stage-0 babel-loader

Update package.json

Update your package.json file, add babel-polyfill to devDependencies:

"devDependencies": {
  "babel-core": "^6.0.20",
  "babel-polyfill": "^6.0.16",
  "babel-preset-es2015": "^6.0.15",
  "babel-preset-stage-0": "^6.0.15"
}

Update .babelrc

You don’t need to make any changes to the .babelrc file. It should look like this:

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

Update your JavaScript files

Make sure you are using async/await syntax. For example:

"use strict";

export default async function foo() {
  var s = await bar();
  console.log(s);
}

function bar() {
  return "bar";
}

In your startup file

In your startup file, make sure you are registering Babel and babel-polyfill:

require("babel-core/register");
require("babel-polyfill");

For users using webpack, please follow @Cemen’s suggestion and add babel-polyfill Set to the first value of the entry array in your webpack configuration file:

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

  output: {
    filename: 'bundle.js'       
  },

  module: {
    loaders: [
      { test: /\.jsx?$/, loader: 'babel', }
    ]
  }
};

For Mocha testing, use the following:

mocha --compilers js:babel-core/register --require babel-polyfill

Following these steps you should Ability to resolve "regeneratorRuntime is not defined" errors and use async/await syntax.

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