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 those present in the node_modules folder that are
not listed as any package's dependency 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, extraneous modules are pruned automatically, so you'll
only need this command with the --production flag. However, in the real
world, operation is not always "normal". When crashes or mistakes happen,
this command can help clean up any resulting garbage.