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Webpacker ships with babel - a JavaScript compiler so you can use next generation JavaScript, today. The Webpacker installer sets up a standard babel.config.js file in your app root, which will work great in most cases because of @babel/preset-env.

Following ES6/7 features are supported out of the box:

  • Async/await.
  • Object Rest/Spread Properties.
  • Exponentiation Operator.
  • Dynamic import() - useful for route level code-splitting
  • Class Fields and Static Properties.

We have also included core-js to polyfill features in the older browsers.

Don't forget to add these lines into your main entry point:

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

Dynamic/Lazy Chunk Loading

For this section, you need Webpack and Webpacker 4. Then enable SplitChunks as it is explained in docs/webpack.

Dynamic code splitting enables you to conditionally request/run only the JS that you need. For example, if your site has a searchBarComponent on every page, you can reduce the page overhead by deferring the request for the searchBarComponent code until after the page has loaded, until the user has scrolled it into view, or until the user has clicked on an element.

 function loadSearchBarComponent() {
   return import(/* webpackChunkName: "searchBarComponent" */ './pathTo/searchBarComponent')

The comment you see above (/* webpackChunkName */) is not arbitrary, it is one of webpacks magic comments. They can be used to fine-tune import() with settings such as defer or prefetch.

Warning: You should not attempt to dynamically load anything from your packs/ folder. Instead, try to make your pack scripts a hub from which you dynamically load non-pack scripts.

Module import vs require()

While you are free to use require() and module.exports, we encourage you to use import and export instead since it reads and looks much better.

import Button from 'react-bootstrap/lib/Button'

// or
import { Button } from 'react-bootstrap'

class Foo {
  // code...

export default Foo
import Foo from './foo'

You can also use named export and import

export const foo = () => console.log('hello world')
import { foo } from './foo'
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