背景：
vue项目初步构建好，配置好路由之后启动，页面全空白，控制台报错
app.js:167 Uncaught TypeError: Cannot read properties of undefined (reading 'install')
at Function.Vue.use (vue.runtime.esm.js?c320:5739:1)
at eval (index.js?5aa4:19:1)
at Module../src/router/index.js (app.js:95:1)
at webpack_require (app.js:164:33)
at fn (app.js:420:21)
at eval (main.js:4:65)
at Module../src/main.js (app.js:85:1)
at webpack_require (app.js:164:33)
at app.js:1345:109
at Function.webpack_require.O (app.js:210:23)
原因
vue-router版本不对，将原本的版本卸载后，重新下载
解决方案
先卸载之前的vue-router：
npm uninstall vue-router
下载指定版本的vue-router
npm i vue-router@3.1.3
