React Nexus

Isomorphic React apps done ~~right~~ well. Server-side rendering, data prefetching, SEO for free.

Nexus Flux

React Nexus is closely related to Nexus Flux, although Nexus Flux works without React Nexus.

React Nexus takes a webapp, made with React components using Nexus Flux, and orchestrates everything to achieve server-side rendering, data prefetching, SEO and truly isormophic apps for free.

What does 'truly isomorphic' mean ?

Truly isomorphic means that your app can actually be rendered on the server. It means in particular that it can fetch data asynchronously, which React.renderToString can't achieve on its own. Without React Nexus (or a very closely similar app design), you need to fetch all the data BEFORE rendering the React tree, which means that you need to know, only from the request url at the top level, what data your components will need. This violates the component-oriented design of most React apps. You most likely want to define data dependency at the component level, not the router level. Thats exactly what React Nexus allows you to do.

Example

The React docs suggest that you perform data fetching in componentDidMount. Besides the fact that componentDidMount is never called when doing server-side rendering, it wouldn't work anyway: data fetching is asynchronous, and renderToString is synchronous. Which means that by the time your HTTP request is resolved, renderToString has already returned.

Here's how you would do it using React Nexus:

Define a root component using @root(createNexus). createNexus returns an object mapping to instances of Nexus Flux clients. Each of these instances abstracts an asynchronous data backend.
Define components using @component(getNexusBindings). getNexusBindings returns an object mapping flux stores to props keys.
Render the app on the server using Nexus.renderToString. It will resolve asynchronously, and return { html, data } where html is the fully generated HTML (with dependencies resolved), and data a serialization of the prefeteched data so you can serve it to the client.
On the client, bootstrap your root component using the injected data.

Example (using LocalFlux as a placeholder, but you can use SocketIOFlux to use remote stores):

import Nexus from 'react-nexus';

// root component decorator
@Nexus.root(({ data }) => {
  // init some flux stores
  const stores = {
    // if the value is already in data, reuse it, otherwise initialize it
    '/counters': new Remutable(data && data['/counters'] || { clicks: 0 }),
  };

  const server = new LocalFlux.Server(stores);
  const client = new LocalFlux.Client(server);

  // define some actions
  server.on('action', ({ path, params }) => {
    if(path === '/click') {
      const counters = stores['/counters'];
      counters.set('clicks', counters.get('clicks') + 1);
      // updates the stores
      server.dispatchUpdate('/counters', counters.commit());
    }
  });

  // define some clean-up logic
  const lifespan = new Lifespan();
  lifespan.onRelease(() => {
    client.lifespan.release();
    server.lifespan.release();
  });

  const nexus = { local: client };
  // export the nexus and a lifespan object to clean things up later
  return { nexus, lifespan };
})
// component decorator
@Nexus.component(() => ({
  // bind the 'counters' props to the '/counter' store of the 'local' flux
  // provide a default value in case fetching fails somehow
  counters: ['local://counters', { clicks: NaN }],
}))
class App extends React.Component {
  static propTypes = {
    nexus: React.PropTypes.object.isRequired,
    counters: Nexus.PropTypes.Immutable.Map,
  };

  click() {
    const { nexus } = this.props;
    const { local } = nexus;
    local.dispatchAction('/click', {});
  }

  render() {
    const { counters } = this.props;
    const clicks = counters.get('clicks');
    return <button onClick={() => this.click()>
      I have been clicked {clicks} times.
    </button>;
  }
}

// on the server
Nexus.renderToString(<App />)
.then(({ html, data }) => {
  serveHtmlAndDataToClient(html, data);
});

// on the client
React.render(<App data={getInjectedData()} />);

Composition and reactive data fetching

One of the nice features of React Nexus is that it enables chaining. You can define a component that depends on data which is the result of nested queries. For example, let's imagine we want to fetch the list of users in our database, then fetch the profile of each user, and render a component that depends on all this stuff (contrived example).

// the result from this query...
@component({
  users: ['remote://users', {}]
})
// is injected here...
@component(({ users }) =>
  users.mapEntries(([userId, user]) =>
    [`user:${userId}`, [`remote://users/${userId}/profile`, {}]]
  ).toObject()
))
class Users extends React.Component {
  // ... this component will receive all the users,
  // and their updates.
}

In addition to be dead numb to perform nested data-fetching, you get reactive data fetching for free. Whenever a piece of data is updated somewhere in the @component chain, the dependencies are properly diffed and updated accordingly. In this case, if remote://users is updated to add a new user, then this user is injected into the next @component, which in turn subscribes to the updates of this user, and injects it into Users.

API

The API is very concise. There are only a few core functions and some useful helps.

`renderToString(element)`

element is a React.Component with the @root decorator.

Asynchronously renders the App. Returns a Promise for { html, data } where html is the fully-rendered HTML, and data is a serializable object with you can pass to the client (eg. using <script> injection).

`renderToStaticMarkup(element)`

Exactly like renderToString, but generates clean HTML, like React.renderToStaticMarkup.

`@root(createNexus)`

React.Component class decorator.

createNexus is function which takes the props of the components, and returns an object { nexus, lifespan }. nexus is an object mapping flux names to flux clients. lifespan should have a release method which will be called when the framework is done with your nexus so you can clean up after yourself.

@root returns a higher-order component. However, it will transfer all its props (except for the special prop data) to the underlying component. It should be used at the top level of a components hierachy, as expected by renderToString.

`@component(getNexusBindings)`

React.Component class decorator.

getNexusBindings is a function which takes the props of the component, and returns an object mapping each key to [storeLocation, defaultValue] where storeLocation takes the form ${fluxName}:/${storeKey}. For example, local://route will map to the /route store of the local flux. defaultValue is an optional value to use when the fetching is pending or has failed.

@component returns a higher-order component. However, it will transfer all its props to the underlying component, as well as a special nexus property, which you can use to dispatch actions on a particular flux. It should be used on components in a React hierarchy of which the root has the @root decorator.

The enhanced component will be passed the values of the bindings as props (using the same keys as the bindings object). Whenever a binding value is updated, the component will receive new props. Whenever the wrapper components props change, the bindings are updated to reflect the new return value of getNexusBindings.

This means in particular that you can typecheck fetched values using propTypes, as well as react to updates using componentWillReceiveProps.

Much like render, getNexusBindings should be very fast and without side effects, as it will be called multiple times during the lifecycle of a component.

@component and @root can be applied on the same component, but @root must be applied first since @component only works in a component hierarchy with a @root-decorated root.

@component support slight convenience variations. @component without any argument doesn't have bindings except for this.props.nexus, to dispatch actions. @component(obj) is a convenience shorthand for @component(() => obj) for when the bindings don't depend on the props of the component.

`PropTypes.Immutable.Map`

Convenient PropTypes validator for Immutable.Map (delegating to Immutable.Map.isMap), to typecheck the results of bindings.

Example:

static propTypes = {
  route: Nexus.PropTypes.Immutable.Map,
}

How to inject data in the client

This is the relatively tricky part, at least if you're not used to ismorphic javascript tricks. One simple solution is to inject the data object in the clients' main function using an injected <script> tag, as follows:

// --- SERVER PART ---
import jsescape from 'jsesc';

renderToString(<App />)
.then(({ html, data }) => {
  sendToClient(`<html>
    <head>
      ...
    </head>
    <body>
      <div id='AppRoot'>${html}</div>
      <script src='client.js'></script>
      <script>
        (function(data) {
          // startClient is a global exported by client.js
          startClient(data, document.getElementById('AppRoot'));
        })(JSON.parse(${jsescape(JSON.stringify(data))}));
      <script>
    </body>
  </html>`);
});

// --- CLIENT PART ---
window.startClient = (data, node) => React.render(<App data={data} />, node);

Usage

This module is written in ES6/7. You will need babel to run it.

eTorAken/react-nexus