Update npm included in node@10

How do I update the version of npm that is included in node@10?
Alternatively, how do I make macOS use a manually installed npm (in /usr/local/lib/node_modules/npm)?

Thanks!

npm can update itself:
npm install -g npm

Caveat: I’ve not tried this nor have ever had the need to run a version of npm not provided by node.

That only works if I put the manually installed npm first in the path or manually change the symlink of /usr/local/bin/npm. The former breaks calling node itself, the latter might break during updates.