I know there are a lot of questions regarding this npm package installing, but I couldn't find the exact relevant answer.
I have already installed npm and also developed a few applications in my Visual Studio. Every time, before developing the new project of Angular, do we need to install npm again by typing "npm install -g @angular/cli" in cmd?
Once you have installed @angular/cli globally, in the next project you just need run ng new app-name.
This command will create a folder named 'app-name' and then will install all dependencies locally, including @angular/cli.
Installing @angular/cli globally allow you to use 'ng' command everywhere. It's required to install locally, because to your project, some specific @angular/cli version is required and newer versions maybe break.
If your @angular/cli global is newer than the local project version, 'ng' will use the local @angular/cli instead, when you run 'ng serve', for example.
Résumé: after installing using npm install -g @angular/cli, you will need just to run ng new app-name.