update vue version npm

1npm install -g @vue/cli
2# OR
3yarn global add @vue/cli
4

1npm install -g @vue/cli --save
2
3# OR
4yarn global upgrade --latest @vue/cli

1npm install -g vue-cli    //make sure you have node and npm installed 
2vue init webpack <appname>  //  eg:  vue init webpack myapp
3cd <appname>               // cd myapp
4npm install
5npm run dev  //server will start in port 8080