vue-cli 2.x upgrade to version 3.x, 2.x and 3.x version to downgrade command

vue-cli 2.x version upgrade to version 3.x

npm install -g @vue/cli

或者

yarn yarn global add @vue/cli

Downgrading from vue-cli 3.x version to version 2.x

npm install -g @vue/cli-init

或者

yarn global add @vue/cli-init