1：安装命令

yarn add element-ui --save

2:删除

yarn remove element-ui --save

安装如果出现下面问题：

error Couldn't find package "fsevents@~2.3.2" required by "chokidar@^3.5.3" on the "npm" registry.

解决方法：

找到package.json，移除  "dependencies": {}  节点

然后：npm install=>yarn install=>yarn add element-ui,然后会重新生成"dependencies": {} 节点=>然后刚刚移除的内容拷贝到"dependencies": {} 节点下面

=>然后在yarn install(呢时候就不能在npm install了，否则 ERR! While resolving: webapiroots@0.1.0报错)

=>如果要npm install就移除package.json里面的 "element-ui": "^2.15.8"  

=>再次安装element-ui不能用npm install element-ui --save 只能 yarn add element-ui 否则会报错

npm ERR! Fix the upstream dependency conflict, or retry
npm ERR! this command with --force, or --legacy-peer-deps

=>如果yarn add element-ui报下面的错

error An unexpected error occurred: "https://registry.yarnpkg.com/element-ui: connect ETIMEDOUT 104.16.16.35:443".
info If you think this is a bug, please open a bug report with the information provided in "E:\\vscode\\vue\\vue\\vue\\vue\\webapiroots3diyipian\\yarn-error.log".
info Visit https://yarnpkg.com/en/docs/cli/add for documentation about this command.

重复上面的操作

找到package.json，移除  "dependencies": {}  节点，在npm install=>yarn install=>yarn add element-ui,然后会重新生成"dependencies": {} 节点=>然后刚刚移除的内容拷贝到"dependencies": {} 节点下面