Implement basic methods of react server rendering

This article mainly introduces you to the detailed implementation of react server rendering from scratch. The editor thinks it is quite good, so I will share it with you now and give it as a reference. Let’s follow the editor to take a look, I hope it can help everyone.

Preface

When I was writing koa recently, I thought, if part of my code provides API and part of the code supports SSR, then how should I write it? Woolen cloth? (If you don’t want to split it into two services)
And I have also used some server-side rendering in the projects I have written recently, such as nuxt, and I have also worked on next projects. It is true that the development experience is very friendly, but friendly is still friendly. , how is it implemented specifically? Have you ever considered it?

Based on a pragmatic attitude, I chose react as the research object (mainly because Vue has been written too much, which is disgusting). Then I will simply write a react server-side rendering demo at the minimum cost.

Technology stack used

react 16 + webpack3 + koa2

Look at how it implements server-side rendering Yes, here we go!

Why use server-side rendering

Advantages

It’s nothing more than two points

1. SEO friendly

2. Speed ​​up first screen rendering and reduce white screen time

Then the question arises What is SEO

In one sentence, most of the websites we make now are SPA websites. All pages and data come from ajax. When the search engine spider comes to collect the web pages, , found completely empty? So do you think the weight and effect of your website's inclusion are good or bad?

The core of our SEO optimization is also described in the following content:

The following is the key point!

Let the server return the HTML with content to us. If the event occurs, the browser will render it again to mount it

Build the koa environment

Create a new ssr project and initialize npm in the project

mkdir ssr && cd ssr
npm init

In the following code we use syntax such as import jsx, which is not supported by the node environment. So you need to configure babel

Create new files app.js and index.js in the current project, and then

babel’s entrance, the index.js code is as follows

require('babel-core/register')()

require('babel-polyfill')
require('./app')

The entrance to our project, the app.js code is as follows

import Koa from 'koa'
const app = new Koa()

// response
app.use((ctx) => {
 ctx.body = 'Hello Koa'
})

app.listen(3000)
console.log("系统启动，端口：3000")

Create a new .babelrc file in the root directory

Content Yes:

{
 "presets": ["react", "env"]
}

Install the dependencies required above

npm install babel-core babel-polyfill babel-preset-env babel-preset-react nodemon --save-dev
npm i koa --save

Configure startup script

package .json

"scripts": {
 "dev": "nodemon index.js",
}

Here you run npm run dev and open localhost:3000

You will see hello Koa

Yes It is not very simple to start a service

Install React

##

cnpm install react react-dom --save

Create a new app folder in the root directory , and create a new main.js in the folder

The main.js code is as follows

import React from 'react'

export default class Home extends React.Component {
 render () {
  return <p>hello world</p>
 }
}

Before modifying server.js

import Koa from 'koa'
import React from 'react'
import { renderToString } from 'react-dom/server'
import App from './app/main'

const app = new Koa()

// response
app.use(ctx => {
 let str = renderToString(<App />)

 ctx.body = str
})

app.listen(3000)

console.log(&#39;系统启动，端口：8080&#39;)

At this time, npm run dev

You will see hello world appear on the screen

Then open the chrome developer tools to view our Request:

Our simplest react component becomes str and passed in

Here we use a method:

renderToString - In fact, it is to render the component into a string

So far, we have not added events and other interactive behaviors to the component. Let us try it next

Modify main. js code

import React from 'react'

export default class Home extends React.Component {
 render () {
  return <p onClick={() => window.alert(123)}>hello world</p>
 }
}

Refresh our page again, hey, is it useless?

That’s because the backend can only talk about components Rendering into a string of html, event binding and other things need to be performed on the browser side

So how do we bind the event?

Then you will definitely guess that since the server renders a string of html, the way to mount the event is to re-render it once in the browser

Just do it Do

Configure webpack

Create a new webpack.config.js under the root directory

The following is webpack.config. js content:

var path = require('path')
var webpack = require('webpack')

module.exports = {
 entry: {
  main: './app/index.js'
 },
 output: {
  filename: '[name].js',
  path: path.join(__dirname, 'public'),
  publicPath: '/'
 },
 resolve: {
  extensions: ['.js', '.jsx']
 },
 module: {
  loaders: [
   {test: /\.jsx?$/,
    loaders: ['babel-loader'],
   }
  ]
 }
}

The above configuration sets the entry to the app/index.js file

Then we will create one

The following is the code of app/index.js:

import Demo from './main'
import ReactDOM from 'react-dom'
import React from 'react'
ReactDOM.render(<Demo />, document.getElementById(&#39;root&#39;))

Because browser rendering requires mounting the root component to a dom node, the react code given to us Setting up an entrance

There is a problem at this time, that is, the document object does not exist in the node environment, so how to solve it?

does not exist? If it doesn’t exist, then I don’t need it. The core of SSR is to return specific HTML content in the requested URL. I don’t care about events, so I just return the root component directly to renderToString

. Okay

Let’s modify our service code so that the code supports server rendering

Add some dependencies

cnpm i --save koa-static koa-views ejs

1. koa-static： 处理静态文件的中间件

2. koa-views： 配置模板的中间件

3. ejs：一个模板引擎

修改server.js的代码

import Koa from 'koa'
import React from 'react'
import { renderToString } from 'react-dom/server'
import views from 'koa-views'
import path from 'path'

import Demo from './app/main'
const app = new Koa()
// 将/public文件夹设置为静态路径
app.use(require('koa-static')(__dirname + '/public'))
// 将ejs设置为我们的模板引擎
app.use(views(path.resolve(__dirname, './views'), { map: { html: 'ejs' } }))

// response
app.use(async ctx => {
 let str = renderToString(<Demo />)
 await ctx.render(&#39;index&#39;, {
  root: str
 })
})

app.listen(3000)

console.log(&#39;系统启动，端口：8080&#39;)

下面新建我们的渲染模板

新建一个views文件夹

里面新建一个index.html：

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <base href="/client" rel="external nofollow" >
</head>
<body>
  <p id="root"><%- root %></p>
  <script src="/main.js"></script>
</body>
</html>

这个 html 里面可以放一些变量，比如这个，就是等下要放renderToString结果的地方

/main.js则是react构建出来的代码

下面直接来测试一下我们的代码

1. 在 package.json里面

新增：

 "scripts": {
  "dev": "nodemon index.js",
  "build": "webpack"
 },

2. 运行 npm run build， 构建出我们的react代码

3. npm run dev

点击一下代码，是不是会 alert(123)

 tada 撒花，恭喜你，一个最简单服务器渲染就已经完成

到这里核心的思想就都已经讲完了，总结来说就下面三点：

1. 起一个node服务

2. 把react 根组件 renderToString渲染成字符串一起返回前端

3. 前端再重新render一次

原理就是这么简单

但是具体开发的时候还会有各种各样的需求，比如：

1. 不可能我每次改完代码都重新构建看效果吧 => 需要 实时构建

2. create-react-app 都是热更新，你还要刷新是不是太蠢了 => 需要支持热更新

3. 其他一些配套的周边，如： react-router, redux 或者mobx怎么支持呢 => 需要完善的生态

.etc

这些问题都是用完 官方脚手架之后就回不去了的，所以更多的配置可以参考下面的repo（是一个工具链完善的最小实现），欢迎提PR

GitHub - ws456999/koa-react-ssr-starter: to understand && to explain how react ssr works

目前你可以在里面找到 react + react-router + mobx + postcss + 热更新的配置，除了react-router的配置有些差别，其他都跟client端差别不大

相关推荐：

react后端渲染模板引擎noox发布使用方法

React前后端同构防止重复渲染

浏览器渲染性能优化

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