vue installation, and 'webpack-dev-server' is not an internal or external command, nor is it a runnable program or batch file

Nue install vue under Windows: https://www.cnblogs.com/liluxiang/p/9592003.html
Vue project encountered "'webpack-dev-server' is not an internal or external command, nor is it a running program or batch "File" error: https://www.cnblogs.com/shenhaha520/p/9014150.html