npm prune [[<@scope>/]<pkg>...] [--production] [--dry-run] [--json]
This command removes "extraneous" packages. If a package name is provided, then only packages matching one of the supplied names are removed.
Extraneous packages are packages that are not listed on the parent package's dependencies list.
If the --production flag is specified or the NODE_ENV environment variable is set to production, this command will remove the packages specified in your devDependencies. Setting --no-production will negate NODE_ENV being set to production.
If the --dry-run flag is used then no changes will actually be made.
If the --json flag is used then the changes npm prune made (or would have made with --dry-run) are printed as a JSON object.
In normal operation with package-locks enabled, extraneous modules are pruned automatically when modules are installed and you'll only need this command with the --production flag.
If you've disabled package-locks then extraneous modules will not be removed and it's up to you to run npm prune from time-to-time to remove them.