Babel 7 - ReferenceError: regeneratorRuntime is not defined

I have an application that is a node backend and a react frontend.

I get the following error when i try to build/run my node application.

Node: v10.13.0

Error:

> dist/index.js:314 > regeneratorRuntime.mark(function _callee(productId) { > ^ > > ReferenceError: regeneratorRuntime is not defined

.babelrc

{
    "presets": [    [
        "@babel/preset-env", {
          "targets": {
            "node": "current"
          },
        }
      ], "@babel/preset-react"],
    "plugins": [
        "@babel/plugin-proposal-class-properties"
    ]
}

webpack.config.js

{
        mode: "development",
        entry: "./src/index.js",
        target: "node",
        externals: [nodeExternals()], // in order to ignore all modules in node_modules folder
        stats: {
            colors: true
        },
        devtool: "source-map",

        output: {
            path: path.resolve(__dirname, "dist"),
            filename: "index.js",
            sourceMapFilename: "index.js.map"
        },
        module: {
            rules: [
                {
                    enforce: "pre",
                    test: /\.js$/,
                    exclude: /node_modules/,
                    loader: "eslint-loader",
                },
                {
                    test: /\.m?js$/,
                    exclude: /(node_modules|bower_components)/,
                    use: {
                        loader: "babel-loader",
                        options: {
                            presets: ["@babel/preset-env"]
                        }
                    }
                }
            ],
        },
        node: {
            __dirname: false,
            __filename: false,
        },

        "plugins": [
            new CleanWebpackPlugin(),
            new WebpackShellPlugin({
                onBuildStart: [],
                onBuildEnd: ["nodemon dist/index.js"]
            }),
 
        ]

    },

package.json

 "dependencies": {
    "connect": "^3.6.6",
    "cors": "^2.8.5",
    "dotenv": "^6.1.0",
    "express": "^4.16.4",
    "hellojs": "^1.17.1",
    "i18n-iso-countries": "^3.7.8",
    "morgan": "^1.9.1",
    "react": "^16.6.3",
    "react-dom": "^16.6.3",
    "request": "^2.88.0",
    "request-promise-native": "^1.0.5",
    "serve-static": "^1.13.2",
    "vhost": "^3.0.2"
  },
  "devDependencies": {
    "@babel/cli": "^7.1.5",
    "@babel/core": "^7.1.6",
    "@babel/plugin-proposal-class-properties": "^7.1.0",
    "@babel/preset-env": "^7.1.6",
    "@babel/preset-react": "^7.0.0",
    "babel-eslint": "^10.0.1",
    "babel-loader": "^8.0.4",
    "clean-webpack-plugin": "^1.0.0",
    "copy-webpack-plugin": "^4.6.0",
    "css-loader": "^1.0.1",
    "eslint": "^5.9.0",
    "eslint-config-google": "^0.10.0",
    "eslint-loader": "^2.1.1",
    "eslint-plugin-react": "^7.11.1",
    "extract-loader": "^3.0.0",
    "file-loader": "^2.0.0",
    "node-sass": "^4.10.0",
    "sass-loader": "^7.1.0",
    "style-loader": "^0.23.1",
    "webpack": "^4.26.0",
    "webpack-cli": "^3.1.2",
    "webpack-node-externals": "^1.7.2",
    "webpack-shell-plugin": "^0.5.0"
  }

Updated Answer:

If you are using Babel 7.4.0 or newer, then @babel/polyfill has been deprecated. Instead, you will want to use the following at the top of your main js file (likely index.js or similar):

import "core-js/stable";
import "regenerator-runtime/runtime";

Install these packages either with npm:

npm install --save core-js
npm install --save regenerator-runtime    

or with yarn:

yarn add core-js
yarn add regenerator-runtime

Original Answer:

I just encountered this problem and came across the following solution:

In package.json I had @babel/polyfill as a dependency. However, in my index.js (My main js file) I had neglected to place the following line at the the top:

import '@babel/polyfill'

Once I imported it, everything worked fine.

I did not need to install babel-runtime as other answers are suggesting.

Babel 7.4.0 and later

There are two main configurations - one for apps and one for libraries.

Option 1: App

When to use: ✔ for applications ✔ global scope polyfills ✔ smallest bundle size ✔ selective inclusion via targets ✔ No need to process node_modules for polyfills

"presets": [
  [
    "@babel/preset-env",
    {
      "useBuiltIns": "usage", // alternative mode: "entry"
      "corejs": 3, // default would be 2
      "targets": "> 0.25%, not dead" 
      // set your own target environment here (see Browserslist)
    }
  ]
]

Install dependencies:

npm i --save-dev @babel/preset-env

npm i regenerator-runtime core-js // run-time dependencies
// regenerator-runtime: transform (async) generators and `async`/`await`
// core-js: other ECMAScript features like Promise, Set, etc.

@babel/preset-env selectively includes polyfills for targets, specified by a Browserslist query. There are two modes - try usage first (more convenient), else entry (more flexible and robust):

• useBuiltIns 'usage': no need to import anything manually. All polyfills are added automatically based on their code usage in a file.

• useBuiltIns 'entry': Add these import entries once (!) in your app - akin to @babel/polyfill:

  import "regenerator-runtime/runtime";
  import "core-js/stable"; // or more selective import, like "core-js/es/array"
  

Extension

For advanced cases, you might use @babel/transform-runtime (dev) and @babel/runtime (run-time) only for Babel helpers to reduce bundle size a bit more - called helper aliasing.

Option 2: Library

When to use: ✔ for libraries ✔ no global scope pollution ✔ includes all polyfills, not selective ✔ bigger bundle size neglectable

"plugins": [
  [
    "@babel/plugin-transform-runtime",
    {
      "regenerator": true,
      "corejs": 3
    }
  ]
]

Install compile-time and run-time dependencies:

npm i --save-dev @babel/plugin-transform-runtime // only for build phase

npm i @babel/runtime // runtime babel helpers + just regenerator runtime
// OR (choose one!)
npm i @babel/runtime-corejs3 
// also contains other JS polyfills (not only regenerator runtime)
// depends on core-js-pure ("ponyfills"/polyfills that don't pollute global scope)

See @babel/plugin-transform-runtime, @babel/runtime, @babel/runtime-corejs.

Extension

You can additionally use @babel/preset-env for syntax transpilation only, with useBuiltIns: false. As the library option does not use global polyfills, you might want to transpile node_modules as well - see the absoluteRuntime option.

Closing notes

• Breaking Change: @babel/polyfill is deprecated starting with Babel 7.4.0.

• Legacy: If you can't switch to core-js@3, set corejs option to 2 (see migrations). Install @babel/runtime-corejs2 in case of option 2 (@babel/plugin-transform-runtime).

• Excellent summary in #9853 by Jovica Markoski

• Currently, the library approach doesn't take selective targets into account - meaning you take locally scoped polyfills at the price of bigger bundle size (including all polyfills).

• babel-polyfills is a new, experimental approach to inject different polyfills (not just core-js) with different strategies.

• This also allows to selectively include locally scoped polyfills.

There is already a very good answer here (originally posted on the Babel6 question) which I will just translate to Yarn. Basically, you need babel runtime (NOT as a dev dependency) and the plugin transform-runtime

yarn add @babel/runtime 
yarn add -D @babel/plugin-transform-runtime

And, in .babelrc, add:

{
    "presets": ["@babel/preset-env"],
    "plugins": ["@babel/transform-runtime"]
}

I had this error in my react project with webpack 4 and this was preventing the whole project to get rendered.

This is how I solved it:

Install plugin-transform-runtime:

npm install @babel/plugin-transform-runtime -D

Add plugin-transform-runtime to the plugin's list in the .babelrc file:

{
  "presets": [
    "@babel/preset-env",
    "@babel/preset-react"
  ],
  "plugins": [
    ["@babel/transform-runtime"]  // <= Add it here
  ]  
}

I just solved this error when I imported babel-polyfill directly into the file that shows the error, for example, the error says "ReferenceError: regeneratorRuntime is not defined at /dist/models/usersSchema.js", so I use this in my usersSchema.js file:

require("babel-polyfill");

(you can use import "babel-polyfill";as well)

For me worked:

module.exports = {
  presets: [
    [
      '@babel/preset-env',
      {
        targets: {
          esmodules: true,
        },
      },
    ],
  ],
}

You will need to have the regeneratorRuntime.

Install this two packages - babel-plugin-transform-regenerator and babel-polyfill

Add the following Babel configuration via .babelrc

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

React.js Users

If this issue faced you while using react (specifically while trying to use Async/Wait), then Valentino Gagliardi provided a detailed approach on his blog regarding how to address this issue