@isoreact/core

IsoReact ·

IsoReact is a small library to use React and RxJS together to build isomorphic React components.

Features:

• Server-side render fully populated components (not just loading states).
• Hydrate server-side rendered components without hitting APIs for the initial client-side render.
• State management with RxJS.
• Connect state to the component tree via the new context API.

This is a library, not a framework. It is focused on state management and isomorphism and should otherwise stay out of your way.

Installation

npm i -S @isoreact/core

Examples

See isoreact/example

Usage

Create a context to connect an RxJS event stream to your React component:

// profile-context.js
import React from 'react';

export default React.createContext();

Create your React component hierarchy, connecting your context to it using <Connect context={yourContext} />:

// profile.js
import React from 'react';
import {Connect} from '@isoreact/core';
import profileContext from './profile-context';

const ProfileName = () => (
    <section className="profile__name">
        <Connect
            context={profileContext}
            distinctBy={({name}) => name}
        >
            {({name}) => name}
        </Connect>
    </section>
);

const ProfilePhoto = () => (
    <section className="profile__photo">
        <Connect context={profileContext}>
            {({photo}) => (
                <img className="profile__photo-img" src={photo} />
            )}
        </Connect>
    </section>
);

const Profile = () => (
    <section className="profile">
        <ProfileName />
        <ProfilePhoto />
    </section>
);

export default Profile;

You might have noticed distinctBy={({name}) => name} in one of the <Connect /> elements. It's an optional function that uniquely identifies values we're interested in, which is used by Connect to skip duplicate values and therefore duplicate renders.

Define your component's event stream and make it isomorphic:

// iso-profile.js
import PropType from 'prop-types';
import {of as observableOf, combineLatest} from 'rxjs';
import {map} from 'rxjs/operators';
import {isomorphic} from '@isoreact/core';
import Profile from './profile';
import profileContext from './profile-context';
import fetchName from './streams/fetch-name';
import fetchPhoto from './streams/fetch-photo';

const IsoProfile = isomorphic({
    name: 'iso-profile',
    component: Profile,
    context: profileContext,
    getData: (props, hydration) => {
        const {userId} = props;
        
        const name$ = hydration
            ? observableOf({name: hydration.name})
            : fetchName(userId);
        
        const photo$ = hydration
            ? observableOf({photo: hydration.photo})
            : fetchPhoto(userId);
        
        return combineLatest(name$, photo$)
            .pipe(
                map(([name, photo]) => ({
                    // React component rendered with this state as its props
                    state: {
                        name,
                        photo,
                    },
                    
                    // Data rendered alongside the React element in the HTML page
                    hydration: {
                        name,
                        photo,
                    },
                })),
            );
    },
    propTypes: {
        userId: PropType.string.isRequired,
    },
});

export default IsoProfile;

The general contract of getData(props, hydration) is:

• Return an observable that emits objects of the form {state, hydration} where both state and hydration are objects.
• If getData is provided a hydration object, the observable is expected to immediately produce an event.
• Events must contain hydration only when the hydration parameter is not present (i.e. on the server).
• Events can contain hydration when the hydration parameter is present, but it will have no effect.
• Keep hydration small to keep server-side rendered HTML pages small. Only attach the minimum amount of data required to hydrate isomorphic components without them having to fetch data from APIs.

Somewhere on the server:

import React from 'react';
import {renderToHtml} from '@isoreact/core';
import {IsoProfile} from './iso-profile';

// Server-side render an HTML page consisting of the profiles from a list of user IDs.
async function renderUserProfilesPage(userIds) {
    // Generate server-side rendered profile of users
    const htmlArray = await Promise.all(
        userIds.map((userId) => renderToHtml(<IsoProfile userId={userId} />))
    );

    return `<body>${htmlArray.join('')}</body>`;
}

When renderToHtml is called, it will call each isomorphic components' getData function, passing in the isomorphic component's props (in this case, userId). When the stream returned by getData produces its first event (an object consisting of state to inject into the React component and hydration to attach to the HTML page), the isomorphic component's React component will be rendered with the state as its props and the hydration data will be rendered adjacent to it in the HTML page.

Somewhere on the client:

import {hydrate} from '@isoreact/core';
import IsoProfile from './iso-profile';

// Hydrate all instances of iso-profile on the page
hydrate(IsoProfile);

When hydrate is called, it finds all the server-side rendered instances of the isomorphic component in the DOM, reads their attached props and hydration data, then calls getData(props, hydration), expecting the client to render the profiles synchronously, without having to load data from APIs.

Bear in mind that isomorphic components are just React components, so you can use them directly in JSX and you don't even need to initially render them on the server. You could even use this library just for connecting to RxJS.

Support for styled-components

The server-side rendering portion of the above example can be updated as follows:

import React from 'react';
import {renderToHtml, StyledComponentsServerRenderer} from '@isoreact/core';
import {IsoProfile} from './iso-profile';

// Server-side render an HTML page consisting of the profiles from a list of user IDs.
async function renderUserProfilesPage(userIds) {
    // Generate server-side rendered profile of users
    const renderer = new StyledComponentsServerRenderer();
    const htmlArray = await Promise.all(
        userIds.map((userId) => renderToHtml(
            <IsoProfile userId={userId} />,
            {renderer}
        ))
    );

    return `<head>${renderer.getStyleTags()}</head><body>${htmlArray.join('')}</body>`;
}

This uses StyledComponentsServerRenderer as an alternative renderer, which uses ServerStyleSheet from styled-components to gather rendered stylesheets.

Contributing

Contributions are welcome. See CONTRIBUTING.md in this repo for contribution guidelines.