为什么要给 VUE 项目添加 PWA

为什么要添加？因为不管是部署在 IIS，还是 nginx，每次应用部署后，再次访问因为旧的 js 已经不存在，所以页面访问的时候会整个报错，报错的结果就是一个白屏。

为了解决这个问题，我的解决方案是使用 PWA ，这样就可以将 js 缓存到本地，再次发布后，service-worker.js 会使旧的 js 失效，重新请求并缓存 js。

如果对于问题这个有更好的解决方案，务必请大佬指定一二

安装 PWA 的相关依赖包

yarn 安装

yarn add sw-precache-webpack-plugin --dev

yarn add uglify-es --dev

npm 安装

npm install sw-precache-webpack-plugin --dev-dev

npm install uglify-es --dev-dev

添加修改相关配置

下面这些文件忘记出处是哪，Github也能搜到一些，之前写的 PWA 的 Demo 里面拿过来的~

添加 build/service-worker-dev.js

self.addEventListener('install', () => self.skipWaiting())

self.addEventListener('activate', () => {

  self.clients.matchAll({ type: 'window' }).then(windowClients => {

    for (let windowClient of windowClients) {

      // Force open pages to refresh, so that they have a chance to load the

      // fresh navigation response from the local dev server.

      windowClient.navigate(windowClient.url)

    }

  })

})

添加 build/service-worker-prod.js

;(function() {

  'use strict'

  // Check to make sure service workers are supported in the current browser,

  // and that the current page is accessed from a secure origin. Using a

  // service worker from an insecure origin will trigger JS console errors.

  var isLocalhost = Boolean(

    window.location.hostname === 'localhost' ||

      // [::1] is the IPv6 localhost address.

      window.location.hostname === '[::1]' ||

      // 127.0.0.1/8 is considered localhost for IPv4.

      window.location.hostname.match(

        /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/

      )

  )

  window.addEventListener('load', function() {

    if (

      'serviceWorker' in navigator &&

      (window.location.protocol === 'https:' || isLocalhost)

    ) {

      navigator.serviceWorker

        .register('service-worker.js')

        .then(function(registration) {

          // updatefound is fired if service-worker.js changes.

          registration.onupdatefound = function() {

            // updatefound is also fired the very first time the SW is installed,

            // and there's no need to prompt for a reload at that point.

            // So check here to see if the page is already controlled,

            // i.e. whether there's an existing service worker.

            if (navigator.serviceWorker.controller) {

              // The updatefound event implies that registration.installing is set

              var installingWorker = registration.installing

              installingWorker.onstatechange = function() {

                switch (installingWorker.state) {

                  case 'installed':

                    // At this point, the old content will have been purged and the

                    // fresh content will have been added to the cache.

                    // It's the perfect time to display a "New content is

                    // available; please refresh." message in the page's interface.

                    break

                  case 'redundant':

                    throw new Error(

                      'The installing ' + 'service worker became redundant.'

                    )

                  default:

                  // Ignore

                }

              }

            }

          }

        })

        .catch(function(e) {

          console.error('Error during service worker registration:', e)

        })

    }

  })

})()

添加 build/load-minified.js

'use strict'

const fs = require('fs')

const UglifyJS = require('uglify-es')

module.exports = function(filePath) {

  const code = fs.readFileSync(filePath, 'utf-8')

  const result = UglifyJS.minify(code)

  if (result.error) return ''

  return result.code

}

修改 build/webpack.prod.conf.js

首先引用sw-precache-webpack-plugin和build/load-minified

const SWPrecacheWebpackPlugin = require('sw-precache-webpack-plugin')

const loadMinified = require('./load-minified')

为 webpack 插件 HtmlWebpackPlugin 添加参数 serviceWorkerLoader: `<script>${loadMinified( path.join(__dirname, './service-worker-prod.js'))}</script>

  plugins: [

      ....

  new HtmlWebpackPlugin({

      filename:

        process.env.NODE_ENV === 'testing' ? 'index.html' : config.build.index,

      template: 'index.html',

      inject: true,

      minify: {

        removeComments: true,

        collapseWhitespace: true,

        removeAttributeQuotes: true

        // more options:

        // https://github.com/kangax/html-minifier#options-quick-reference

      },

      // necessary to consistently work with multiple chunks via CommonsChunkPlugin

      chunksSortMode: 'dependency',

      serviceWorkerLoader: `<script>${loadMinified( path.join(__dirname, './service-worker-prod.js'))}</script>`

    }),

并在最后添加 SWPrecacheWebpackPlugin 插件

// service worker caching

new SWPrecacheWebpackPlugin({

  cacheId: 'web_pwa',

  filename: 'service-worker.js',

  staticFileGlobs: ['dist/**/*.{js,html,css}'],

  minify: true,

  stripPrefix: 'dist/'

})

在 /index.html 中注入 service-worker.js

<%= htmlWebpackPlugin.options.serviceWorkerLoader %>

如下所示

<body>

  <div id="app"></div>

  <%= htmlWebpackPlugin.options.serviceWorkerLoader %>

  <!-- built files will be auto injected -->

</body>

至此，添加完毕，build 之后查看缓存中是否包含 js 检验结果

注意：PWA 应用需要在本地上运行或者 https 协议下， 要保证你的页面是安全页面。

结语

几分钟就搞定了，然后把之前的一个基于VUE的后台模板项目也升级了，如果有相同需求的可以参考下。

仓库地址：https://github.com/yimogit/me-admin-template

线上预览：https://vue-admin.yimo.link/