npm ls command can be used to list all dependencies for a project.
This will, however, produce an exhaustive list of all dependencies including
dependencies of dependencies. A list this large probably isn’t going to be
of much use.
--depth flag allows you to restrict the depth of the dependency tree
that is generated.
$ npm ls --depth=0
This will produce a list of only the top-level dependencies.
man npm-ls for more details.