SPFx: "You don't seem to have a generator with the name “@microsoft\Sharepoint” installed."

1. install the latest version of node(8 to 10 version of node js)
2. install the latest version of npm: npm i -g npm@next
3. run the following in your cmd window or commander window:

   1-npm uninstall -g chalk
   2-npm uninstall -g loadash
   3-npm uninstall -g tar-fs
   4-npm uninstall -g update-notifier
   5-npm uninstall -g yeoman-generator
   6-npm uninstall -g yosay
   7-npm uninstall -g yo
   8-npm uninstall -g gulp
   9-npm uninstall -g @microsoft/generator-sharepoint
   10-npm install -g chalk
   11-npm install -g loadash
   12-npm install -g tar-fs
   13-npm install -g update-notifier
   14-npm install -g yeoman-generator
   15-npm install -g yosay
   16-npm install -g yo
   17-npm install -g gulp