Modify Create React App's Babel Configuration Without Ejecting

I love using Create React App to spin up an application swiftly, but one annoyance I keep running into is not being able to modify the Babel configuration. Why would you want to do this? Perhaps you want to use some of the latest ES.next features before they’re approved and merged into Create React App. In this case, you could eject the app, but there are several reasons you might not want to.

For this article, we’re going to add both the nullish coalescing operator and optional chaining syntax Babel plugins. These plugins are both excluded from Create React App at the time of writing.

Begin by firing up your terminal and creating a new app with Create React App:

npx create-react-app my-app
cd my-app

The first step may take a while to complete depending on your internet connection. If you do not have npx installed, run npm install --global npx or yarn global add npx and then try the previous step again. We need two separate packages to override the configuration, customize-cra and react-app-rewired. We’re not calling react-app-rewired directly, but it’s a required dependency of customize-cra.

npm i -D customize-cra react-app-rewired

Open package.json in your editor of choice and replace all references to react-scripts under the scripts property with react-app-rewired. Once complete, your scripts should look like this:

"scripts": {
 "start": "react-app-rewired start",
 "build": "react-app-rewired build",
 "test": "react-app-rewired test"
}

Create a new file called config-overrides.js in the project root directory.

touch config-overrides.js

customize-cra has various utility functions you can use to configure virtually all aspects of the Babel and webpack config. In our case, addBabelPlugins is what we need to add both plugins.

Open config-overrides.js and add the following:

const { override, addBabelPlugins } = require("customize-cra");

module.exports = override(
  addBabelPlugins(
    "@babel/plugin-proposal-nullish-coalescing-operator",
    "@babel/plugin-syntax-optional-chaining",
  ),
);

For both of the plugins to work correctly, we’ll need to install the packages.

npm i -D @babel/plugin-proposal-nullish-coalescing-operator @babel/plugin-syntax-optional-chaining

You can now test that it all works by running npm start in your terminal. Open src/App.js, remove all the boilerplate code, and add an expression to verify Babel is transpiling the bundle correctly.

import React from "react";

export default function App() {
  const obj = {};
  const prop = obj.foo?.bar?.() ?? "foo bar";
  return <div className="App">{prop}</div>;
}

In this example, you should see no errors in the webpack output, and foo bar rendered on the screen.