react-chunk

_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

Install

``sh
npm install --save react-chunk
`

`sh
yarn add react-chunk
`

Example

For more detailed examples, take a look at the examples

$3

`js
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 ;
}
}
`

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`js
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 (

);
}

return

Loading...

;
}

const MyComponentsChunk = chunks({
MyComponent: () => import('./my-component'),
MyOtherComponent: () => import('./my-other-component'),
})(MutilImportRenderer);

export default class App extends React.Component {
render() {
return ;
}
}
`

Environment Configuration

It's _recommended_ you configure your development environment with the following plugins.

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Configure your client build.

#### Babel

Add these plugins to your babel configuration.

`sh
npm install --save-dev babel-plugin-syntax-dynamic-import
`

The order of plugins is important.

.babelrc
`json
{
"presets": {...},
"plugins": [
"react-chunk/babel",
"syntax-dynamic-import"
]
}

`

#### Webpack

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

`js
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
})
]

`

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If your application performs SSR, configure your server build.

#### Babel

Add these plugins to your babel configuration.

`sh
npm install --save-dev babel-plugin-dynamic-import-node
`

The order of plugins is important.

.babelrc
`json
{
"presets": {...},
"plugins": [
"react-chunk/babel",
"dynamic-import-node"
]
}

`

Introduction




$3

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.




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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.

`js
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);

`

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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.

`js
function ChunkRenderer(props) {
const {
chunk: {
isLoading,
hasLoaded,
pastDelay,
timedOut,
error,
retry,
loaded,
Imported
},
...restProps
} = prop;

if (hasLoaded) {
return ;
}

if (error) {
return

;
}

if (timedOut) {
return (

This is taking a while..
retry()}>retry?

);
}

if (isLoading && pastDelay) {
return

Loading...

;
}

return null;
}

chunk(() => import('./someComponent'))(ChunkRenderer);
`

To make this all nice, your chunk component receives a
couple different props.


#### Avoiding _Flash Of Loading Component_

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.

`js
chunk(() => import('./components/Bar'), {
delay: 300, // 0.3 seconds
});
`

#### Timing out when the loader is taking too long

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.

`js
chunk(() => import('./components/Bar'), {
timeout: 10000, // 10 seconds
});
`

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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.

#### Chunk rendering without a rendering component

`js

// 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.


#### Rendering multiple chunks

chunks requires a rendering component be provided when invoking the HOC, an error will be thrown if this requirement is not met.




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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.

#### Using chunks for multiple imports

`js
const MultiComponentChunk = chunks({
Bar: () => import('./Bar'),
i18n: () => fetch('./i18n/bar.json').then(res => res.json())
}, {
delay: 300,
// other options here...
})(RequiredRendererComponent);
`




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As an optimization, you can also decide to preload one or more components before being
rendered.

#### Preload a single chunk

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.

`js
const BarChunk = chunk(() => import('./Bar'))();

class MyComponent extends React.Component {
state = { showBar: false };

onClick = () => {
this.setState({ showBar: true });
};

onMouseOver = () => {
BarChunk.preloadChunk();
};

render() {
return (



)
}
}
`

#### Preload multiple chunks

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.

`js
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
})

`

Server-Side Rendering

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.

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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.

`js
import { preloadAll } from 'react-chunk';

preloadAll().then(() => {
app.listen(3000, () => {
console.log('Running on http://localhost:3000/');
});
});
`

#### Configure babel and webpack

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.

#### Tracking which dynamic modules were rendered

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.

`js
import ChunkRecorder from 'react-chunk/Recorder';

app.get('/', (req, res) => {
let renderedChunks = [];

let html = ReactDOMServer.renderToString(
renderedChunks.push(chunkName)}>


);

console.log(renderedChunks);

res.send(...${html}...);
});
`

#### Resolving rendered chunks

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.

`js
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(
renderedChunks.push(chunkName)}>


);

let resources = resolveChunks(chunkData, renderedChunks);

// ...
});
`

We can then render these resources using
}).join('\n')}

${scripts.map(bundle => {
return
}).join('\n')}

);
`

#### Preloading resolved chunks on the client

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.

`js
// 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(, document.getElementById('app'));
}).catch(err => {
// errors can occur if imports timeout or fail
// render an error page
});

`


Now server-side rendering should work perfectly!


API

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A higher-order component for dynamically importing a single resource.

chunk(import: function[, options: Object]): ChunkComponent

`js
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.

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A higher-order component that allows you to load multiple resources in parallel.

chunks(importMap: {[string]: function}[, options: Object]): ChunksComponent


`js
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.




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#### opts.displayName: string

The react display name to assign when creating the HOC.

#### opts.hoistStatics: boolean

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.

#### opts.resolveDefaultImport: (imported, importKey) => mixed

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.

#### opts.retryBackOff: Array

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_.


#### opts.delay: number

Time to wait (in milliseconds) before passing
props.pastDelay to your loading
component. This defaults to 200.

Read more about delays.

#### opts.timeout: number

Time to wait (in milliseconds) before passing
props.timedOut to your loading component.
This is turned off by default.

Read more about timeouts.

#### opts.webpack: function

An optional function which returns an array of Webpack module ids which you can
get with require.resolveWeak.

`js
chunk(() => import('./component'), {
webpack: () => [require.resolveWeak('./Foo')],
});
`

This option can be automated with the Babel Plugin.

#### opts.modules: Array

An optional array with module paths for your imports.

`js
chunk(() => import('./component'), {
modules: ['./my-component']
});
`

This option can be automated with the Babel Plugin.

$3

This is the component returned by chunk.

`js
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.

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This is the component returned by chunks.

`js
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.

$3


#### preloadChunk()

This is a static method that can be used to load the component ahead of time.

`js
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.

Read more about preloading.

#### getChunkLoader()

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()

`js
const ChunkComponent = chunk({...});

ChunkComponent.getChunkLoader();
`

#### onImported(subscriber: (ImportedComponent) => void): () => void

This is a static method that can be used to subscribe for notifications when component has been imported.

Returns an unsubscribe function.

`js
const ChunkComponent = chunk({...});

ChunkComponent.onImported((ImportedComponent) => { / use ImportedComponent / });
`

#### onImportedWithHoist(subscriber: (ImportedComponent) => void): () => void

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.

`js
const ChunkComponent = chunk({...});

ChunkComponent.onImportedWithHoist((ImportedComponent) => { / use ImportedComponent / });
`

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This is the component you pass to the chunk() or chunks() HOC.

`js
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 ;
}

if (error) {
return

;
}

if (timedOut) {
return (

This is taking a while..
retry()}>retry?

);
}

if (isLoading && pastDelay) {
return

Loading...

;
}

return null;
}

`

Read more about loading components

#### chunk.Imported: mixed
> Note the UPPER CASE 'i'
>
> This prop is only passed to chunk components.

It provides access to the default export of the imported resource.

It is only populated when chunk.hasLoaded is true.

#### chunk.imported: Object
> Note the LOWER CASE 'i'
>
> This prop is only passed to chunks components.

It provides access to the default export of the all imported resource, by key.

It is only populated when chunk.hasLoaded is true.


#### chunk.importKeys: Array

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() and chunks() components.

#### chunk.isLoading: boolean

true if the import(s) are currently being loaded, otherwise false.

#### chunk.hasLoaded: boolean

true if the import(s) have been successfully loaded, otherwise false.

#### chunk.error: boolean

A boolean prop passed to WrappedComponent when the loading resource(s) has failed.

`js
function WrappedComponent({chunk}) {
if (chunk.error) {
return

;
} else {
return

Loading...

;
}
}
`

Read more about errors.

#### chunk.timedOut: boolean

A boolean prop passed to WrappedComponent after a set
timeout.

`js
function WrappedComponent({chunk}) {
if (chunk.timedOut) {
return

;
} else {
return

Loading...

;
}
}
`

Read more about timeouts.

#### chunk.pastDelay: boolean

A boolean prop passed to WrappedComponent after a set
delay.

`js
function WrappedComponent({chunk}) {
if (chunk.pastDelay) {
return

;
} else {
return null;
}
}
`

Read more about delays.

#### chunk.loaded: mixed

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.

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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.

`js
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:

`js
// During module initialization...
const ChunkComponent = chunk(...);

class MyComponent extends React.Component {
componentDidMount() {
// ...
}
}
`

Bad:

`js
// ...

class MyComponent extends React.Component {
componentDidMount() {
// During app render...
const ChunkComponent = chunk(...);
}
}
`

> Note: preloadAll() will not work if you have more than one
> copy of react-chunk in your app.

Read more about preloading on the server.

$3

Check for modules that are already loaded in the browser and call the matching
WrappedComponent.preload methods.

`js
import { preloadReady } from 'react-chunk';
preloadReady().then(() => {
ReactDOM.hydrate(, document.getElementById('app'));
});
`

Read more about preloading on the client.

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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.

`js
import ChunkRecorder from 'react-chunk/Recorder';
let renderedChunks = [];

let html = ReactDOMServer.renderToString(
renderedChunks.push(chunkName)}>


);

console.log(renderedChunks);
`

Read more about capturing rendered modules.

Babel Plugin

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:

`json
{
"plugins": ["react-chunk/babel"]
}
`

Input

`js
import { chunk, chunks } from 'react-chunk';

const ChunkMyComponent = chunk(() => import('./MyComponent'));

const ChunkComponents = chunks({
One: () => import('./One'),
Two: () => import('./Two'),
});
`

Output

`js
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.

Webpack Plugin

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.

`js
// 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.

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Required, the destination file for writing react-chunk module data

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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.

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A method exported by react-chunk/webpack for converting chunks to
resources.

`js
import { resolveChunks } from 'react-chunk/webpack';

let resources = resolveChunks(chunkData, renderedChunks);
`

Read more about mapping modules to bundles.

FAW

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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.

`js
// chunkOptions.js
const defaultChunkOpts = {
delay: 200,
timeout: 10,
};

export default defaultChunkOpts;
`

`js
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.

`js
import MyComponentChunk from './MyComponentChunk';
import ChunkRenderer from './ChunkRenderer';

const MyAutoRetryComponentChunk = MyComponentChunk({
retryBackOff: [200, 300]
})(ChunkRenderer);

export default class App extends React.Component {
render() {
return ;
}
}
`

$3

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:

`js
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(



...
${styles.map(style => {
return
}).join('\n')}

${scripts.map(script => {
return
}).join('\n')}



);
``