Aravind Balla/writings

(P)reacting on the server side

September 30, 2018

It takes time to realise Server-side rendering is amazing.😁 It was the same for me. You get a ton of benefits with it. Mainly, first meaningful paint of the webpage is quick. It still has to download the js to make it interactive. But, users will not be staring at white (empty) pages for long.

As you might know, Preact is the 3KB alternative to React. It is a bit faster than React and very less in size. The API is mostly same and easy to adapt if you are coming from React.

Let’s see how we can do that using Node on the server. We will be using preact-router for the routing at the client side.

This is the repo that I have created, if you want to follow along.


Create an empty directory and npm init it!

Now, we install the necessary things.

1yarn add preact preact-router preact-render-to-string express
3yarn add -D webpack webpack-cli babel-core babel-cli babel-loader
4babel-preset-env babel-plugin-transform-react-jsx babel-register

There are a few new packages that are helping us here.

preact-render-to-string - This will help us render the App to string so that we can include this in the HTML that we send out to the client.

babel-register - helps in transpiling ES6 code at run time on the server.

Webpack πŸ”·

Look at the repo to see how the project is structured. client folder contains the Preact code and the webpack is configured to generate a build from that folder to a file.

1module.exports = {
2 entry: {
3 app: './client/index.js',
4 },
5 output: {
6 path: path.join(__dirname, 'dist'),
7 filename: '[name].js',
8 },
9 module: {
10 rules: [
11 {
12 test: /.js$/,
13 loader: 'babel-loader',
14 },
15 ],
16 },

Server πŸš€

The main file is index.js here where it requires babel to be present at runtime and help in transpiling code.

2 presets: ['env'],
3 plugins: [['transform-react-jsx', { pragma: 'h' }]],

{"pragma": "h"} is given as an option to the transform-react-jsx babel plugin because we are dealing with Preact and createElement is h() in it.

Babel can do the magic once you tell this to it. ✨

Now we have server.js where the rendering logic is present.

1const express = require('express');
2const { h } = require('preact');
3const renderToString = require('preact-render-to-string');
4const path = require('path');
5const chalk = require('chalk');
7const App = require('./client/App');
9const app = express();
10const port = 8080;
12app.use(express.static(path.join(__dirname, 'dist')));
16app.get('*', (req, res) => {
17 const html = renderToString(<App />);
19 res.send(`
20<!DOCTYPE html>
21<html lang="en">
23 <meta charset="UTF-8">
24 <meta name="viewport" content="width=device-width, initial-scale=1.0">
25 <meta http-equiv="X-UA-Compatible" content="ie=edge">
26 <title>Preact SSR</title>
29 <div id="app">${html}</div>
30 <script src="./app.js"></script>
33 `);
36console.log(`Server started at http://localhost:${port}`));

See how we are generating html and including it in res.send(). We include the Webpack output, app.js, as a script tag. As we have set express.static as the dist directory, Express will serve that folder as well.

That’s it.


Run node index.js to see the magic. πŸŽ‰

Take Care

Aravind Balla

By Aravind Balla who is a cool human, buiding things for himself, and sometimes for others. You should hit him up on Twitter!