React Deps lets you to declare dependencies on component level in composable, unintrusive and unopinionated way. And it's isomorphic to boot!
import { load } from 'react-deps';
import store from './store';
const getPosts = () => {
return store.posts
? store.posts
: fetch('http://jsonplaceholder.typicode.com/posts/')
.then((response) => response.json())
.then((data) => {
store.dispatch('GET_POSTS', data);
return data;
});
};
const Component = (props) => <h1>Posts: {JSON.stringify(props.posts)}</h1>;
export default load({
posts: (props, isInitialRender) => getPosts()
})(Component);Actually, the above is pretty much it. The library is a simple HOC (higher order component) called load. It takes a single argument, an object with its keys mapped to props passed to your component. The values are functions which are called with two optional arguments props and initialRender (more on it later) and the function should either return a plain value or a promise. The values are passed down to your component as props when resolved.
React Deps has no internal dependencies (aside from React) and is very lightweight. Since it's nothing more than a simple HOC, it's library-agnostic and can be used with any solution.
/**
* server
*/
import express from 'express';
import { renderToString } from 'react-deps';
import { App } from './App';
import { store } from './store';
const app = express();
app.get('/', function(req, res) {
//use React Deps renderToString instead of ReactDOMServer.renderToString
renderToString(<App />).then((html) => {
res.send(`
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>React Deps</title>
<script>
window.__INITIAL_STATE__ = ${JSON.stringify(store.getState())}
</script>
</head>
<body>
<div id="app">${html}</div>
<script type="application/javascript" src="app.js"></script>
</body>
</html>
`);
});
});
app.listen(9000, function() {
console.log('*** This is an isomorphic react server ***');
});/**
* client
*/
import { render } from 'react-deps'
import { App } from './App'
import { store } from './store'
//simple assignment for clarity's sake, normally store state is set through its own API
store = window.__INITIAL_STATE__ || {}
//use React Deps render instead of ReactDOM.render
render(<App />, document.querySelector('#app'))The above is all you need to have a fully working isomorphic application with React Deps. The only thing you need to do is to use load to load your component dependencies and make sure that when on the client, your dependencies will get data from your store instead of fetching it from the server again, as illustrated in the basic example at top of the page.
Also notice that React Deps is not dependent of any library implementation and therefore it's up to you to hydrate your data from server to client. This allows React Deps to be very composable and pluggable for almost any architecture you may use. Don't worry though, it's very easy to do as shown in the above example.
Your dependency functions also get a second argument isInitialRender which can be used for optimizing your requests. isInitialRender is set to true on the server and also when rendering on the client for the first time, otherwise it's set to false. This makes it possible to write optimized code such as:
import { load } from 'react-deps';
import { store } from './store';
import MyComponent from './MyComponent'
const getPost = (postId, useCurrentValue) => {
return useCurrentValue && store.posts && store.posts[postId]
? store.posts[postId]
: fetch(`http://jsonplaceholder.typicode.com/posts/${postId}`)
.then((response) => response.json())
.then((data) => {
store.dispatch('GET_POST', data);
return data;
});
};
export default load({
post: (props, isInitialRender) => {
const useCurrentValue = isInitialRender;
return getPost(props.postId, useCurrentValue);
}
})(MyComponent)React is capable of isomorphic applications but it wasn't likely built with all the complexities in mind. One issue which comes up quite often in the React community is how to properly handle populating data on the server. The issue is that renderToString is a synchronous operation while data fetching is generally asynchronous. This means that you need to have some mechanism in place to populate your stores/models before rendering and hydrating your data for client to use. Some solutions include:
- Fetching and populating data on routing level, taking advantage of static component methods
- Populating generic data on the server and having client fetch more dynamic and specific data
- Calling
renderToStringmultiple times
The first two solutions are not ideal. It's ideal to let components declare what data they need to function and have the same declarations work both on client and server. With the first two solutions, you are very likely declaring data for components out of their own scope, which may lead to tightly coupled, implicit code. You also possibly have to maintain data dependencies in multiple places which is not optimal.
React Deps utilizes the third approach. This is accomplished by using its own asynchronous version of renderToString. When renderToString is called on the server, React will render the component tree and React Deps will keep track of all the dependencies your components are using. Once all the dependencies have been resolved, React Deps will call renderToString again as new dependencies can cause React to render more components. This is repeated until two subsequent renderToString calls return the same dependencies. It's also notable that React Deps caches all the dependencies so they are only called once no matter how many renderToString calls are made, keeping it very fast even with deep component trees.