npm adduser
Create or verify a user named <username> in the npm registry, and
save the credentials to the .npmrc file.
The username, password, and email are read in from prompts. This command cannot be scripted. If you think you need to script the creation of new users, or the authorization of existing ones, without human intervention, please rethink your use case. That's a very bad idea.
You may use this command to change your email address, but not username or password.
You may use this command multiple times with the same user account to authorize on a new machine.