Vue --version solve problems when installing or vue vue is not an internal command

1. attempt vue global configuration environment variable to find the path vue.cmd, and then configure it.

　　　　Question: In file search, did not find vue.cmd, failed.

　　1.npm above sea level and -g

　　　　Global update the version of npm, as 5.xx

　　2.npm she vue-cli -g

　　　　At this point, enter vue --version check for the version number, if not, continue to the next step, if you can, the problem is solved

　　3.cnpm i vue-cli -g

　　　　vue.cmd file appears, the path is: C: \ Users \ ada \ AppData \ Roaming \ npm \ vue.cmd

　　Finally, execute in cmd: vue -V, the version number of 2.9.2 appear to solve the problem.