Warning when installing npm using MacPorts I don't understand/what to do with?

I just installed npm10 with MacPorts. At the end of the installation I got this warning: It is not recommended to install packages globally. But if you do so please be aware that they won't get cleaned up when you deactivate or uninstall npm10. Globally installed packages will remain in /opt/local/lib/node_modules/ until you manually delete them. AFAIK, Everything I install using MacPorts is by default installed globally, and it is complicated or not possible to not install globally, isn't it? What is the recommended "solution" to this warning? Couldn't find any documentation at MacPorts.