error ‘ElementUI‘ is defined but never used no-unused-vars

在使用Vue引入ElementUI后，运行项目，报错 

error  'ElementUI' is defined but never used  no-unused-vars

You may use special comments to disable some warnings.
Use // eslint-disable-next-line to ignore the next line.
Use /* eslint-disable */ to ignore all warnings in a file.
ERROR in [eslint]

排查了半天，发现是在mian.js文件中少加入了 Vue.use(ElementUI);

Vue.use(ElementUI);