安装el：

npm install element-plus --save

npm i element-ui -S

1.缺少package.json

npm WARN saveError ENOENT: no such file or directory, open 'E:\htdocs2\vue\eldemo\package.json'

npm notice created a lockfile as package-lock.json. You should commit this file.

npm init 通过初始化生成；

2.core-js版本过低：

npm install -g core-js@3.1.1

npm install --save  -g core-js@^3.3

npm WARN deprecated core-js@2.6.12: core-js@<3.3 

3.安装vue；

npm install -g cnpm --registry=https://registry.npm.taobao.org

cnpm install  vue@^2.5.16

npm WARN element-ui@2.15.2 requires a peer of vue@^2.5.17