react 首屏載入優化，原本是在入口HTML檔案中載入loading動畫，但是部署在測試環境上的時候一直無法顯示loading的部分，也是奇怪了，我們測試環境的部署一直跟本地的都不太一樣，內外網的轉發多次，總感覺會丟掉一些檔案。

本次採取的優化方法就是，按需載入，首先需要下載依賴，yarn add react-loadable, index.js頁面程式碼如下：

import React from 'react';
import ReactDOM from 'react-dom';
import { Switch, HashRouter, Route } from 'react-router-dom';

import Loadable from 'react-loadable'
import Loading from './component/common/loading'
// import './App.css';
import './index.css';

import registerServiceWorker from './registerServiceWorker';
// import Main from './component/main/main'
let Main = Loadable({
    loader:()=>import('./component/main/main'),
    loading: Loading
})
let Question = Loadable({
    loader:()=> import('./component/question/question'),
    loading: Loading
})
let Egg = Loadable({
    loader:()=> import('./component/egg/egg'),
    loading: Loading
})
let Result = Loadable({
    loader:()=> import('./component/result/result'),
    loading: Loading
})
let Email = Loadable({
    loader:()=> import('./component/email/email'),
    loading: Loading
})

// import Question from './component/question/question'
// import Egg from './component/egg/egg'
// import Result from './component/result/result'
// import Email from './component/email/email'





// document.onreadystatechange = function listen(){
//     if(document.readyState == 'complete'){
//         ReactDOM.render(
//             <div className="App">
//                 <HashRouter>
//                     <Switch>
//                         <Route exact path="/" component={Main}/>
//                         <Route exact path="/question" component={Question}/>
//                         <Route exact path="/egg/:kyc" component={Egg}/>
//                         <Route exact path="/result" component={Result}/>
//                         <Route exact path="/email" component={Email}/>
//                     </Switch>
//                 </HashRouter>
//             </div>,
//             document.getElementById('root'));
//     }else{
//         ReactDOM.render(
//             <div style={{fontSize:'40px',color:'#000'}}>
//                 loading
//             </div>,
//             document.getElementById('root'));
//     }
// }
// document.onreadystatechange = listen
ReactDOM.render(
    <div className="App">
        <HashRouter>
            <Switch>
                <Route exact path="/" component={Main}/>
                <Route exact path="/question" component={Question}/>
                <Route exact path="/egg/:kyc" component={Egg}/>
                <Route exact path="/result" component={Result}/>
                <Route exact path="/email" component={Email}/>
            </Switch>
        </HashRouter>
    </div>,
    document.getElementById('root'));

registerServiceWorker();

 本次的css檔案同樣也是很大，採取的原則就是拆分開各個css檔案，不同的元件再引入需要的css，前面頁面已經引入的css檔案後面不需要再引入

2.nginx 開啟gzip，親測試開啟之後壓縮了很多，截圖如下：

 css,js檔案壓縮來超過一半，

具體是在nginx的配置檔案中下面配置檔案：

gzip on;

gzip_buffers 32 4k;

gzip_comp_level 6;

gzip_min_length 200;

gzip_types text/css text/xml application/javascript;

gzip_vary on;

具體配置截圖為：