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4.8.7 • Public • Published


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Provides a Fusion.js application class that is pre-configured with React universal rendering.

The App class from this package should typically be used instead of App from fusion-core if you want React as the rendering engine, and you want it to be configured to do both server and client rendering.

This package allows you to have deeply nested components with asynchronous dependencies and have everything just work with server-side rendering.

The typical use-case is when a deeply-nested component needs to have a resource fetched from a remote HTTP server, such as GraphQL or REST API. Since renderToString is synchronous, when you call it on your app, this component won't render correctly.

One solution is to have a central router at the root of your application that knows exactly what data needs to be fetched before rendering. But this solution doesn't fit the component-based architecture of a typical React app. You want to declare data dependencies at the component level, much like your declare your props.

This is exactly what fusion-react does: it allows you to declare asynchronous dependencies at the component level, and make them work fine with server-side rendering as well as client-side rendering.

If an application grows too much in size, one way to help reduce the size of the initial download is to split parts of the application into separate bundles and download those only when they are needed. This technique is known as bundle splitting and fusion-react provides tools to do it easily.

Table of contents


yarn add fusion-react


// ./src/main.js
import React from 'react';
import App from 'fusion-react';

const Hello = () => <div>Hello</div>;

export default function() {
  return new App(<Hello />);



import App from 'fusion-react';

A class that represents an application. An application is responsible for rendering (both virtual dom and server-side rendering). The functionality of an application is extended via plugins.


const app: App = new App(
  (el: ReactElement),
  (render: ?(el: ReactElement, ctx: Context) => any)
  • el: ReactElement - a template root. In a React application, this would be a React element created via React.createElement or a JSX expression.
  • render: ?Plugin<Render>|Render - Optional. Defines how rendering should occur. A Plugin should provide a value of type Render
    • type Render = (el:ReactComponent, ctx: Context) => any


app.register((plugin: Plugin));
app.register((token: Token), (plugin: Plugin));
app.register((token: Token), (value: any));

Call this method to register a plugin or configuration value into a Fusion.js application.

You can optionally pass a token as the first argument to associate the plugin/value to the token, so that they can be referenced by other plugins within Fusion.js' dependency injection system.


app.middleware((deps: Object<string, Token>), (deps: Object) => Middleware);
app.middleware((middleware: Middleware));
  • deps: Object<string,Token> - A map of local dependency names to DI tokens
  • middleware: Middleare - a middleware
  • returns undefined

This method is a shortcut for registering middleware plugins. Typically, you should write middlewares as plugins so you can organize different middlewares into different files.


app.enhance((token: Token), (value: any => Plugin | Value));

This method is useful for composing / enhancing functionality of existing tokens in the DI system.


await app.cleanup();

Calls all plugin cleanup methods. Useful for testing.

  • returns Promise


React Hooks were introduced in React v16.8. Make sure you are using a compatible version.

import {useService} from 'fusion-react';
import {ExampleToken} from 'fusion-tokens';

function Component() {
  const service = useService(ExampleToken);
  return (
    <button onClick={service}>Invoke Service</button>
  • token: Token<TService> - Required. The token used to look up the registered plugin that resolves to TService.
  • service: TService - The service provided by the registered plugin.

If no plugin has been registered to this token, an exception is thrown. If you intend you use an optional Token, you can suppress this exception by using useService(Token.optional).


import {ServiceConsumer} from 'fusion-react';
import {ExampleToken} from 'fusion-tokens';

function Component() {
  return (
    <ServiceConsumer token={ExampleToken}>
      {service => (
        <button onClick={service}>Invoke Service</button>
  • token: Token<TService> - Required. The token used to lookup the registered plugin.
  • children: TService => React.Element<any> - Required. Render prop that is passed the registered service. Should return the React Element to render.
  • service: TService - The service provided by the registered plugin.

This is the same pattern as the useService hook. Opt for using the hook. ServiceConsumer is provided as a replacement for any legacy Context usage that may exist. Use Token.optional to if you intend to use an optional plugin.


import {useContext} from 'react';
import {FusionContext} from 'fusion-react';

function Component() {
  const ctx = useContext(FusionContext);
  // ...
  • ctx: Context The Fusion middleware context for this request. Instance of React.createContext()

FusionContext is provided in the case where a plugin may be memoized based on request, i.e.:

const session = Session.from(ctx);

In this case, you will need to not only use useService to get the service you are interested in, but you will also have to get the FusionContext to pass into your service.


import {withServices} from 'fusion-react';
import {ExampleToken} from 'fusion-tokens';

function Component({exampleProp}) {
  return (

export default withServices(
    example: ExampleToken,
  deps => ({ exampleProp: deps.example }),
  • deps: {[string]: Token<TService>} - Required. Object whose values are Tokens.
  • mapServicesToProps: {[string]: TService} => {[string]: any} - Optional. Function receives an object whose values are resolved services and returns an object to spread as props to a component. If omitted, the deps object is returned as-is.
  • HOC: Component => Component - An HOC is returned that passes the result of mapServicesToProps to it's Component argument.

withServices is a generic HOC creator that takes a set of Tokens and an optional mapping function and returns a higher-order component that will pass the resolved services into the given Component.


import {split} from 'fusion-react';

const Component = split({load, LoadingComponent, ErrorComponent});
  • load: () => Promise - Required. Load a component asynchronously. Typically, this should make a dynamic import() call. The Fusion compiler takes care of bundling the appropriate code and de-duplicating dependencies. The argument to import should be a string literal (not a variable). See webpack docs for more information.
  • LoadingComponent - Required. A component to be displayed while the asynchronous component hasn't downloaded
  • ErrorComponent - Required. A component to be displayed if the asynchronous component could not be loaded
  • defer: boolean - Defaults to false. If defer is false split bundle is also rendered on the server.


import {prepare} from 'fusion-react';

const Component = prepare(element);
  • Element: React.Element - Required. A React element created via React.createElement
  • Component: React.Component - A React component

Typically, you shouldn't need to call prepare yourself, if you're using App from fusion-react. The only time you might need to call it is if you imported App from fusion-core to implement a custom Application class.

The prepare function recursively traverses the element rendering tree and awaits the side effects of components decorated with prepared (or dispatched).

It should be used (and await-ed) before calling renderToString on the server. If any of the side effects throws, prepare will also throw.

Timing information will be collected in ctx.timing.prepass - the number of prepasses required as well as the duration of each prepass.


import {prepared} from 'fusion-react';

const hoc = prepared(sideEffect, opts);
  • sideEffect: (props: Object, context: Object) => Promise - Required. When prepare is called, sideEffect is called (and awaited) before continuing the rendering traversal.
  • opts: {defer, boundary, componentDidMount, componentWillReceiveProps, componentDidUpdate, forceUpdate, contextTypes} - Optional
    • defer: boolean - Optional. Defaults to false. If the component is deferred, skip the prepare step.
    • boundary: boolean - Optional. Defaults to false. Stop traversing if the component is defer or boundary.
    • componentDidMount: boolean - Optional. Defaults to true. On the browser, sideEffect is called when the component is mounted.
    • [TO BE DEPRECATED] componentWillReceiveProps: boolean - Optional. Defaults to false. On the browser, sideEffect is called again whenever the component receive props.
    • componentDidUpdate: boolean - Optional. Defaults to false. On the browser, sideEffect is called again right after updating occurs.
    • forceUpdate: boolean - Optional. Defaults to false.
    • contextTypes: Object - Optional. Custom React context types to add to the prepared component.
  • hoc: (Component: React.Component) => React.Component - A higher-order component that returns a component that awaits for async side effects before rendering.
    • Component: React.Component - Required.
Prepared component props
  • effectId: string - Used to enable effectFn to be called multiple times when rendering the same component.
const PreparedComponent = prepared(effectFn)(SomeComponent);

// effectFn called only once
const app1 = (
    <PreparedComponent />
    <PreparedComponent />
    <PreparedComponent />

// effectFn called for each rendered PreparedComponent
const app2 = (
    <PreparedComponent effectId="1" />
    <PreparedComponent effectId="2" />
    <PreparedComponent effectId="3" />


import {exclude} from 'fusion-react';

const NewComponent = exclude(Component);
  • Component: React.Component - Required. A component that should not be traversed via prepare.
  • NewComponent: React.Component - A component that is excluded from prepare traversal.

Stops prepare traversal at Component. Useful for optimizing the prepare traversal to visit the minimum number of nodes.


import {SkipPrepareToken} from 'fusion-react';

app.register(SkipPrepareToken, true);

Skips the prepare render of the application, which is responsible for running side effects in prepared statements.


[DEPRECATED] When using useService, ServiceConsumer, or withServices it is no longer necessary to add a Provider to your application. Services are made available through a generic Context instance in the fusion-react app class.


import {Provider} from 'fusion-react';
const ProviderComponent: React.Component = Provider.create((name: string));
  • name: string - Required. The name of the property set in context by the provider component. name is also used to generate the displayName of ProviderComponent, e.g. if name is foo, ProviderComponent.displayName becomes FooProvider
  • returns ProviderComponent: React.Component - A component that sets a context property on a class that extends BaseComponent


[DEPRECATED] When using useService, ServiceConsumer, or withServices it is no longer necessary to register a ProviderPlugin in place of a Plugin. This is handled within the fusion-react app class.

import {ProviderPlugin} from 'fusion-react';

Creates a plugin that wraps the React tree with a context provider component.


const plugin: Plugin = ProviderPlugin.create(
  (name: string),
  (plugin: Plugin),
  (ProviderComponent: React.Component)
  • name: string - Required. The name of the property set in context by the provider component. name is also used to generate the displayName of ProviderComponent, e.g. if name is foo, ProviderComponent.displayName becomes FooProvider
  • plugin: Plugin - Required. Creates a provider for this plugin.
  • ProviderComponent: React.Component - Optional. An overriding provider component for custom logic
  • Plugin: Plugin - A plugin that registers its provider onto the React tree


[DEPRECATED] See withServices for a generic HOC. For applications still using ProvidedHOC, note that this will work without registering a ProviderPlugin to wrap your Plugin, but it is recommended to migrate to using useService, ServiceConsumer, or withServices instead.

import {ProvidedHOC} from 'fusion-react';

Creates a HOC that exposes a value from React context to the component's props.


const hoc: HOC = ProvidedHOC.create(
  (name: string),
  (mapProvidesToProps: Object => Object)
  • name: string - Required. The name of the property set in context by the corresponding provider component.
  • mapProvidesToProps: Object => Object - Optional. Defaults to provides => ({[name]: provides}). Determines what props are exposed by the HOC.
  • token: Token<TService> - Optional. By supplying a token, the HOC will return a component that uses the useService hook instead of the legacy Context API.
  • returns hoc: Component => Component


Using a service

// src/plugins/my-plugin.js
import {createPlugin, createToken} from 'fusion-core';

export const MyToken = createToken('my-token');
export const MyPlugin = createPlugin({
  provides() {
    return console;

// src/main.js
import {MyPlugin, MyToken} from './plugins/my-plugin.js';

export default (app: FusionApp) => {
  app.register(MyToken, MyPlugin);
  // ...

// components/some-component.js
import {MyToken} from '../plugins/my-plugin.js';
import {useService} from 'fusion-react';

exoprt default Component (props) {
  const console = useService(MyToken);
  return (
    <button onClick={() => console.log('hello')}>Click me</button>

Disabling server-side rendering

Sometimes it is desirable to avoid server-side rendering. To do that, override the render argument when instantiating App:

// src/main.js
import App from 'fusion-react';
import ReactDOM from 'react-dom';

const render = __NODE__
  ? () => '<div id="root"></div>'
  : el => ReactDOM.render(el, document.getElementById('root'));
const app = new App(root, render);

Data fetching

// src/main.js
import React from 'react';
import App from 'fusion-react';
import Example from './components/example';
import UserAPI from './api'

export default () => {
  const app = new App(<Example />);


  return app;

// src/components/example.js
import {prepared} from 'fusion-react';

function Example({name}) {
  return <div>Hello, {name}</div>;

export default prepared(() => fetch('/api/user/1'))(Example);

// src/api.js
import {createPlugin} from 'fusion-core';

export default createPlugin({
  middleware() {
    return (ctx, next) => {
      if (ctx.path === '/api/user/1') {
        ctx.body = {name: 'Bob'};
      return next();

Bundle splitting

// src/main.js
import App from 'fusion-react';
import root from './components/root';

export default () => {
  return new App(root);

// src/components/root.js
import React from 'react';
import {split} from 'fusion-react';

const LoadingComponent = () => <div>Loading...</div>;
const ErrorComponent = () => <div>Error loading component</div>;
const BundleSplit = split({
  load: () => import('./components/hello');

const root = (
    <div>This is part of the initial bundle</div>
    <BundleSplit />

export default root;

// src/components/hello.js
export default () => (
    This is part of a separate bundle that gets loaded asynchronously
    when the BundleSplit component gets mounted




npm i fusion-react

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