Universal Async Component

Async component that works in server and client. It will allows code splitting that works for universal apps.

What is this?

This is solving the hard problem of mixing code splitting and server side rendering. To avoid "flash of contents" in the initial page load server must include dynamic chunks required to render that screen in the HTML response. Using this library and adding corresponding components to your build system you can achieve that.

Example project

See the example repo

Usage

import { getComponentAsync } from 'universal-async-component';

const AsyncHelloWorld = getComponentAsync({ loader: () => import('./hello') });

const App = () => <AsyncHelloWorld />

Server side rendering

To make server-side rendering work you should update your server code to collect additional required chunks and also update your Webpack config to replace import() calls with something special that makes all of this work.

1. Add `CaptureChunks`

Wrap you app with CaptureChunks in your server renderer. You need to provide Webpack client side stats to it. Also, pass an empty array

const additionalChunks = [];
var htmlString = ReactDOM.renderToString(
    <CaptureChunks statsChunks={clientStats.chunks} additionalChunks={additionalChunks}>
        <App />
    </CaptureChunks>
);

After above code is run, additionalChunks is populated with all chunkIds that is required to render current App.

Use Webpack StatsPlugin you can write the stats to disk:

new StatsPlugin({
    filename: 'client-stats.json',
    fields: ['chunks', 'publicPath', 'assets'],
})

2. Use `additionalChunks`

Use additionalChunks retrieved from CaptureChunks to append required chunks

res.send(`
<html>
    <body>
        <div id="root">${htmlString}</div>
        <script src="webpack-bootstrap.js"></script>
        ${additionalChunks.map(chunkId => `<script src="${chunksId}.client.js"></script>`)}
        <script src="client.js"></script>
    </body>
</html>
`)

Note that additional chunks must come before the main bundle and after Webpack bootstrap script. It's easy to extract out Webpack bootstrap by using CommonsChunkPlugin plugin:

new webpack.optimize.CommonsChunkPlugin({
    names: ['bootstrap'],
    filename: 'webpack-bootstrap.js',
    minChunks: Infinity
}),

3. Add `"string-replace-loader"`

Add "string-replace-loader" before any of other loaders in your client and server Webpack config and require options from "universal-async-component":

const { stringReplaceLoaderOptions } = require('universal-async-component');
const config = {
    rules: [
        test: /\.jsx?/,
        use: {
            loader: "string-replace-loader",
            options: stringReplaceLoaderOptions,
        },
    ],
}

Note: this will go away once React can render async components

lyft/universal-async-component