The project npm run dev created by vue-cli runs very slowly

The project npm run dev created by vue-cli just started to run normally, and then suddenly it took a long time to run. It was later discovered that it was the cause of cnpm. Once npm i failed to install the package, so I used cnpm i to install the package, and it was very slow to run the project after the package was installed.

Solution:删除node_modules文件，cnpm i重新安装包。