Code splitting with minimal boiler plate
A higher order component for loading components with dynamic imports.
This is a fork of react-loadable, differences and new features include:
- A modified API to support new features
- Full render control using a HOC wrapped component
- Improved re-use of import components
- Improved support for route code splitting
- Pre-loading all chunks required to render an entire route
- Option to hoist static methods of imported components
- Option to enable retry support with backoff
- Manually invoking a retry after timeout or error
- Support for react-router-config code splitting
This enables both component and route code splitting
npm install --save react-chunk
yarn add react-chunk
For more detailed examples, take a look at the examples
import { chunk } from 'react-chunk';
// It can be this easy!
const MyComponentChunk = chunk(() => import('./my-component'))();
export default class App extends React.Component {
render() {
return <MyComponentChunk />;
}
}
import { chunks } from 'react-chunk';
// A component for rendering mutilple imports
function MutilImportRenderer(props) {
const {
chunk: {
isLoaded,
imported: {
MyComponent,
MyOtherComponent
}
},
...restProps
}) = props;
if (isLoaded) {
return (
<div>
<MyComponent {...restProps} />
<MyOtherComponent {...restProps} />
</div>
);
}
return <div>Loading...</div>;
}
const MyComponentsChunk = chunks({
MyComponent: () => import('./my-component'),
MyOtherComponent: () => import('./my-other-component'),
})(MutilImportRenderer);
export default class App extends React.Component {
render() {
return <MyComponentsChunk />;
}
}
It's recommended you configure your development environment with the following plugins.
Configure your client build.
Add these plugins to your babel configuration.
npm install --save-dev babel-plugin-syntax-dynamic-import
The order of plugins is important.
.babelrc
{
"presets": {...},
"plugins": [
"react-chunk/babel",
"syntax-dynamic-import"
]
}
The react-chunk webpack plugin will write the chunk module data to a file required for server-side rendering.
The webpack CommonsChunkPlugin
is required to allow non entry point chunks to be pre-loaded on the client.
Add the plugins to your client webpack plugins
import webpack from 'webpack';
import { ReactChunkPlugin } from 'react-chunk/webpack';
plugins: [
new ReactChunkPlugin({
filename: path.join(__dirname, 'dist', 'react-chunk.json')
}),
new webpack.optimize.CommonsChunkPlugin({
name: 'manifest',
minChunks: Infinity
})
]
If your application performs SSR, configure your server build.
Add these plugins to your babel configuration.
npm install --save-dev babel-plugin-dynamic-import-node
The order of plugins is important.
.babelrc
{
"presets": {...},
"plugins": [
"react-chunk/babel",
"dynamic-import-node"
]
}
When you use import()
with Webpack 2+, it will
automatically code-split for
you with no additional configuration.
This means that you can easily experiment with new code splitting points just
by switching to import()
and using React Chunk. Figure out what performs
best for your app.
Its often useful to assign names to webpack chunks. This can be achieved easily using inline code comments.
Be aware that naming chunks impacts how webpack bundles your code. You should read about webpack code splitting.
import { chunk, chunks } from 'react-chunk';
const AppChunk =
chunk(() => import(/* webpackChunkName: "App" */ './app'))();
const TimeChunk =
chunks({
Calendar: () => import(/* webpackChunkName: "calendar" */ './calendar'),
Clock: () => import(/* webpackChunkName: "clock" */ './clock'),
})(TimeRenderer);
Rendering a static "Loading..." doesn't communicate enough to the user. You also need to think about error states, timeouts, retries, and making it a nice user experience.
As a developer, you can easiliy re-use import rendering logic when importing a single component. Renderering components for multiple components don't require much more effort.
function ChunkRenderer(props) {
const {
chunk: {
isLoading,
hasLoaded,
pastDelay,
timedOut,
error,
retry,
loaded,
Imported
},
...restProps
} = prop;
if (hasLoaded) {
return <Imported {...restProps } />;
}
if (error) {
return <div>An error occured</div>;
}
if (timedOut) {
return (
<div>
This is taking a while..
<a onClick={() => retry()}>retry?</a>
</div>
);
}
if (isLoading && pastDelay) {
return <div>Loading...</div>;
}
return null;
}
chunk(() => import('./someComponent'))(ChunkRenderer);
To make this all nice, your chunk component receives a couple different props.
Sometimes components load really quickly (< 200ms) and the loading screen only quickly flashes on the screen.
A number of user studies have proven that this causes users to perceive things taking longer than they really have. If you don't show anything, users perceive it as being faster.
So your rendering component will also get a pastDelay
prop
which will only be true once the component has taken longer to load than a set
delay.
This delay defaults to 200ms
but you can also customize the
delay in chunk
and chunks
.
chunk(() => import('./components/Bar'), {
delay: 300, // 0.3 seconds
});
Sometimes network connections suck and never resolve or fail, they just hang there forever. This sucks for the user because they won't know if it should always take this long, or if they should try refreshing.
The rendering component will receive a
timedOut
prop which will be set to true
when the
loader
has timed out.
However, this feature is disabled by default. To turn it on, you can pass a
timeout
option to chunk
and chunks
.
chunk(() => import('./components/Bar'), {
timeout: 10000, // 10 seconds
});
By default chunk
and chunks
will render the default
export of each returned import.
If you want to customize this behavior you can use the
resolveDefaultImport
option.
// Notice the HOC is invoked with no component
const MyComponentChunk = chunk(() => import('./myComponent'))();
When no rendering component is provided, null
is rendered until the component hasLoaded.
chunks
requires a rendering component be provided when invoking the HOC, an error will be thrown if this requirement is not met.
To make it easier to load multiple resources in parallel, you can use
chunks
.
When using chunks
a rendering component must be provided when invoking the HOC.
const MultiComponentChunk = chunks({
Bar: () => import('./Bar'),
i18n: () => fetch('./i18n/bar.json').then(res => res.json())
}, {
delay: 300,
// other options here...
})(RequiredRendererComponent);
As an optimization, you can also decide to preload one or more components before being rendered.
For example, if you need to load a new component when a button gets pressed, you could start preloading the component when the user hovers over the button.
The components created by chunk
and chunks
expose a
static preload
method which does exactly this.
const BarChunk = chunk(() => import('./Bar'))();
class MyComponent extends React.Component {
state = { showBar: false };
onClick = () => {
this.setState({ showBar: true });
};
onMouseOver = () => {
BarChunk.preloadChunk();
};
render() {
return (
<div>
<button
onClick={this.onClick}
onMouseOver={this.onMouseOver}>
Show Bar
</button>
{this.state.showBar && <BarChunk />}
</div>
)
}
}
This approach can be used to load all the chunks required for rendering a route on the client, and ensure that all chunks are loaded before rendering the route.
This makes it easier to handle errors, instead of having to render an error for each failed component on the page (which may result in the user seeing many error messages) you can simply render an error page for the user - and allow the user to retry the previous action if desired.
import { preloadChunks } from 'react-chunk';
const FooChunk = chunk(() => import('./Foo'))();
const BarChunk = chunk(() => import('./Bar'))();
preloadChunks([
FooChunk.getChunkLoader(),
BarChunk.getChunkLoader(),
]).then(() => {
// use 'setState()' to render using the loaded components
}).catch(err => {
// handle timeouts, or other errors
})
When you go to render all these dynamically loaded components, what you'll get is a whole bunch of loading screens.
This really sucks, but the good news is that React Chunk is designed to make server-side rendering work as if nothing is being imported dynamically.
The first step to rendering the correct content from the server is to make sure that all of your chunk components are already loaded when you go to render them.
To do this, you can use the preloadAll
method. It returns a promise that will resolve when all your chunk
components are ready.
import { preloadAll } from 'react-chunk';
preloadAll().then(() => {
app.listen(3000, () => {
console.log('Running on http://localhost:3000/');
});
});
Ensure you have configured babel and webpack for both client and server builds.
The babel plugin adds additional information to all of your chunk
and chunks
.
Next we need to find out which chunks were used to perform the server render.
For this, there is the Recorder
component which can
be used to record all the chunks used for rendering.
import ChunkRecorder from 'react-chunk/Recorder';
app.get('/', (req, res) => {
let renderedChunks = [];
let html = ReactDOMServer.renderToString(
<ChunkRecorder addChunk={chunkName => renderedChunks.push(chunkName)}>
<App/>
</ChunkRecorder>
);
console.log(renderedChunks);
res.send(`...${html}...`);
});
In order to make sure that the client loads all the resources required by the server-side render, we need to resolve the chunks that Webpack created.
First we need to configure Webpack to write the chunk data to a file. Use the React Chunk Webpack plugin.
Then we can use the plugin output to determine the chunks required for the client render. To determine the files required for each chunk, import the resolveChunks
method from react-chunk/webpack
and the data from Webpack.
import ChunkRecorder from 'react-chunk/Recorder';
import { resolveChunks } from 'react-chunk/webpack'
import chunkData from './dist/react-chunk.json';
app.get('/', (req, res) => {
let renderedChunks = [];
let html = ReactDOMServer.renderToString(
<ChunkRecorder addChunk={chunkName => renderedChunks.push(chunkName)}>
<App/>
</ChunkRecorder>
);
let resources = resolveChunks(chunkData, renderedChunks);
// ...
});
We can then render these resources using <script>
and <link>
tags in our HTML.
It is important that the script files are included before the main entry point, so that they can be loaded by the browser prior to the app rendering.
However, as the Webpack manifest (including the logic for parsing chunks) lives in the main chunk, it will need to be extracted into its own chunk.
This is easy to do with the CommonsChunkPlugin, add it to your webpack plugins configuration.
// webpack.config.js
export default {
plugins: [
//...other webpack plugins
new webpack.optimize.CommonsChunkPlugin({
name: 'manifest',
minChunks: Infinity
})
]
}
- Ensure the
manifest.js
is loaded before all other webpack scripts. - Ensure the main entry point (in this example,
main.js
) is loaded after all other webpack scripts.
let resources = getBundles(chunkData, renderedChunks);
let styles = resources.filter(bundle => bundle.file.endsWith('.css'));
let scripts = resources.filter(bundle => bundle.file.endsWith('.js'));
res.send(`
<!doctype html>
<html lang="en">
<head>
${styles.map(bundle => {
return `<link rel="stylesheet" href ="/dist/${bundle.file}"></script>`
}).join('\n')}
</head>
<body>
<div id="app">${html}</div>
<!-- Load the manifest FIRST -->
<script src="/dist/manifest.js"></script>
<!-- Then, load all resolved scripts -->
${scripts.map(bundle => {
return `<script src="/dist/${bundle.file}"></script>`
}).join('\n')}
<!-- Load the main entry point LAST -->
<script src="/dist/main.js"></script>
</body>
</html>
`);
We can use the preloadReady()
method on the
client to preload the chunk components that were included on the page.
Like preloadAll()
, it returns a promise,
which on resolution means that we can hydrate our app.
// src/entry.js
import React from 'react';
import ReactDOM from 'react-dom';
import { preloadReady } from 'react-chunk';
import App from './components/App';
preloadReady().then(() => {
ReactDOM.hydrate(<App/>, document.getElementById('app'));
}).catch(err => {
// errors can occur if imports timeout or fail
// render an error page
});
A higher-order component for dynamically importing a single resource.
chunk(import: function[, options: Object]): ChunkComponent
import { chunk } from 'react-chunk';
const ChunkComponent = chunk(() => import('./Bar'), {
delay: 200,
timeout: 10000,
})([WrappedComponent]);
This returns a ChunkComponent. The WrappedComponent
for a chunk
is optional, but recommended for complete control of the rendering. The WrappedComponent
will be passed an additional single prop chunk
, that provides all state required to render the imported resource.
A higher-order component that allows you to load multiple resources in parallel.
chunks(importMap: {[string]: function}[, options: Object]): ChunksComponent
import { chunks } from 'react-chunk';
const ChunksComponent = chunks({
Foo: () => import('./Foo'),
Bar: () => import('./Bar')
}, {
// define options here...
delay: 200,
timeout: 10000,
})(WrappedComponent);
This returns a ChunksComponent. The WrappedComponent
for a chunks
is required to control rendering of all imported resources. The WrappedComponent
will be passed an additional single prop chunk
, that provides all state required to render the imported resource.
The react display name to assign when creating the HOC.
true
to hoist non-react static methods of the imported component to the HOC. Defaults to false
.
Note that the static methods are only hoisted after the component is loaded (obviously) - if you're using hoistStatics: true
on a component its recommended that you preload
(or preloadChunks
) the component to avoid invoking static methods that have not yet been assigned to the HOC.
Using this option with chunks
is not supported and will result in an error.
By default, the .default
export of the imported resource is returned to the Imported
property (for chunk
) or the imported
property (for chunks
).
The importKey
is only passed for chunks
.
Allows automatic retry for failed imports using the assigned backOff.
When used in conjuntion with timeout
, retry attempts will be invoked after the configured timeout
value has expired.
For example: [250, 500]
will result in the first retry attempt starting 250ms after the first timeout
or error
. The second retry will start 500ms after the second timeout or error.
Time to wait (in milliseconds) before passing
props.pastDelay
to your loading
component. This defaults to 200
.
Time to wait (in milliseconds) before passing
props.timedOut
to your loading
component.
This is turned off by default.
An optional function which returns an array of Webpack module ids which you can
get with require.resolveWeak
.
chunk(() => import('./component'), {
webpack: () => [require.resolveWeak('./Foo')],
});
This option can be automated with the Babel Plugin.
An optional array with module paths for your imports.
chunk(() => import('./component'), {
modules: ['./my-component']
});
This option can be automated with the Babel Plugin.
This is the component returned by chunk
.
const ChunkComponent = chunk({
// ...
});
Props passed to this component will be passed straight through to the
wrapped component, in additional to a chunk
prop that includes all data required for rendering the imported resource.
This is the component returned by chunks
.
const ChunksComponent = chunks({
// ...
});
Props passed to this component will be passed straight through to the
wrapped component, in additional to a chunk
prop that includes all data required for rendering the imported resources.
This is a static method that can be used to load the component ahead of time.
const ChunkComponent = chunk({...});
ChunkComponent.preloadChunk();
This returns a promise, but you should avoid waiting for that promise to resolve to update your UI. In most cases it creates a bad user experience.
This is a static method that can be used to obtain a reference to the components loader. It should be used in conjuntion with preloadChunks()
const ChunkComponent = chunk({...});
ChunkComponent.getChunkLoader();
This is a static method that can be used to subscribe for notifications when component has been imported.
Returns an unsubscribe
function.
const ChunkComponent = chunk({...});
ChunkComponent.onImported((ImportedComponent) => { /* use ImportedComponent */ });
This is a static method that can be used to subscribe for notifications when component has been imported where hoistStatics: true
.
Note: this requires hoistStatics: true
Returns an unsubscribe
function.
const ChunkComponent = chunk({...});
ChunkComponent.onImportedWithHoist((ImportedComponent) => { /* use ImportedComponent */ });
This is the component you pass to the chunk()
or chunks()
HOC.
function WrappedComponent(props) {
const {
chunk: {
isLoading,
hasLoaded,
pastDelay,
timedOut,
error,
retry,
loaded,
importKeys,
Imported // - only for 'chunk()'
// imported - only for 'chunks()'
},
...restProps
} = prop;
if (hasLoaded) {
return <Imported {...restProps } />;
}
if (error) {
return <div>An error occured</div>;
}
if (timedOut) {
return (
<div>
This is taking a while..
<a onClick={() => retry()}>retry?</a>
</div>
);
}
if (isLoading && pastDelay) {
return <div>Loading...</div>;
}
return null;
}
Read more about loading components
Note the UPPER CASE 'i'
This prop is only passed to
chunk
components.
It provides access to the default export of the import
ed resource.
It is only populated when chunk.hasLoaded
is true
.
Note the LOWER CASE 'i'
This prop is only passed to
chunks
components.
It provides access to the default export of the all import
ed resource, by key.
It is only populated when chunk.hasLoaded
is true
.
For chunks()
, an array of the key names used for imports.
For chunk()
, it will always be an empty array
This can be used to create a generic rendering component that can be used to render both
chunk()
andchunks()
components.
true
if the import(s) are currently being loaded, otherwise false
.
true
if the import(s) have been successfully loaded, otherwise false
.
A boolean prop passed to WrappedComponent
when the loading resource(s) has failed.
function WrappedComponent({chunk}) {
if (chunk.error) {
return <div>Error!</div>;
} else {
return <div>Loading...</div>;
}
}
A boolean prop passed to WrappedComponent
after a set
timeout
.
function WrappedComponent({chunk}) {
if (chunk.timedOut) {
return <div>Taking a long time...</div>;
} else {
return <div>Loading...</div>;
}
}
A boolean prop passed to WrappedComponent
after a set
delay
.
function WrappedComponent({chunk}) {
if (chunk.pastDelay) {
return <div>Loading...</div>;
} else {
return null;
}
}
This is considered a "low-level" API property, the loaded
prop provides raw access to all imported resources. This can be used in scenarios where an imported resource includes multiple exports that you need to access.
This will call all of the
WrappedComponent.preload
methods recursively
until they are all resolved. Allowing you to preload all of your dynamic
modules in environments like the server.
import { preloadAll } from 'react-chunk';
preloadAll().then(() => {
app.listen(3000, () => {
console.log('Running on http://localhost:3000/');
});
});
It's important to note that this requires that you declare all of your chunk components when modules are initialized rather than when your app is being rendered.
Good:
// During module initialization...
const ChunkComponent = chunk(...);
class MyComponent extends React.Component {
componentDidMount() {
// ...
}
}
Bad:
// ...
class MyComponent extends React.Component {
componentDidMount() {
// During app render...
const ChunkComponent = chunk(...);
}
}
Note:
preloadAll()
will not work if you have more than one copy ofreact-chunk
in your app.
Read more about preloading on the server.
Check for modules that are already loaded in the browser and call the matching
WrappedComponent.preload
methods.
import { preloadReady } from 'react-chunk';
preloadReady().then(() => {
ReactDOM.hydrate(<App/>, document.getElementById('app'));
});
Read more about preloading on the client.
A component for reporting which chunks were used for rendering.
Accepts an addChunk
prop which is called for every chunkName
that is
rendered via React Chunk.
import ChunkRecorder from 'react-chunk/Recorder';
let renderedChunks = [];
let html = ReactDOMServer.renderToString(
<ChunkRecorder addChunk={chunkName => renderedChunks.push(chunkName)}>
<App/>
</ChunkRecorder>
);
console.log(renderedChunks);
Read more about capturing rendered modules.
Providing opts.webpack
and opts.modules
for
every chunk component is a lot of manual work to remember to do.
Instead you can add the Babel plugin to your config and it will automate it for you:
{
"plugins": ["react-chunk/babel"]
}
Input
import { chunk, chunks } from 'react-chunk';
const ChunkMyComponent = chunk(() => import('./MyComponent'));
const ChunkComponents = chunks({
One: () => import('./One'),
Two: () => import('./Two'),
});
Output
import { chunk, chunks } from 'react-chunk';
const ChunkMyComponent = chunk(
() => import('./MyComponent'),
{},
{
webpack: () => [require.resolveWeak('./MyComponent')],
modules: ['./MyComponent']
}
});
const ChunkComponents = chunks({
One: () => import('./One'),
Two: () => import('./Two'),
},
{},
{
webpack: () => [require.resolveWeak('./One'), require.resolveWeak('./Two')],
modules: ['./One', './Two']
}
});
Read more about declaring modules.
In order to send the right bundles down when rendering server-side, you'll need the React Chunk Webpack plugin to provide you with a mapping of modules to bundles.
// webpack.config.js
import { ReactChunkPlugin } from 'react-chunk/webpack';
export default {
plugins: [
new ReactChunkPlugin({
filename: './dist/react-chunk.json',
}),
],
};
This will create a file (opts.filename
) which you can import to map modules
to bundles.
Required, the destination file for writing react-chunk module data
Optional, an array of webpack chunk names to exclude from the module data
By ignoring the main entry point (ie: main
or index
) only required module data is included in the output.
Read more about mapping modules to bundles.
A method exported by react-chunk/webpack
for converting chunks to
resources.
import { resolveChunks } from 'react-chunk/webpack';
let resources = resolveChunks(chunkData, renderedChunks);
Read more about mapping modules to bundles.
Specifying the same loading
component or delay
every time you use
chunk()
or chunks()
gets repetitive fast. Instead you can wrap chunk
and chunks
with your
own Higher-Order Component (HOC) to set default options.
// chunkOptions.js
const defaultChunkOpts = {
delay: 200,
timeout: 10,
};
export default defaultChunkOpts;
import { chunk chunks } from 'react-chunk';
import Loading from './my-loading-component';
import defaultChunkOpts form './chunkOptions';
export default function MyComponentChunk(opts = {}) {
return chunk(
() => import('./my-component'),
Object.assign({}, defaultChunkOpts, opts)
);
};
Then you can specify additional options
and a WrappedComponent
when you go to use it.
import MyComponentChunk from './MyComponentChunk';
import ChunkRenderer from './ChunkRenderer';
const MyAutoRetryComponentChunk = MyComponentChunk({
retryBackOff: [200, 300]
})(ChunkRenderer);
export default class App extends React.Component {
render() {
return <MyAutoRetryComponentChunk />;
}
}
When you call resolveChunks
, it may return file types other than
JavaScript depending on your Webpack configuration.
To handle this, you should manually filter down to the file extensions that you care about:
let resources = resolveChunks(stats, modules);
let styles = resources.filter(bundle => bundle.file.endsWith('.css'));
let scripts = resources.filter(bundle => bundle.file.endsWith('.js'));
res.send(`
<!doctype html>
<html lang="en">
<head>
...
${styles.map(style => {
return `<link href="/dist/${style.file}" rel="stylesheet"/>`
}).join('\n')}
</head>
<body>
<div id="app">${html}</div>
<script src="/dist/manifest.js"></script>
${scripts.map(script => {
return `<script src="/dist/${script.file}"></script>`
}).join('\n')}
<script src="/dist/main.js"></script>
</body>
</html>
`);