A note on external dependencies

Once you initialize your component, you can install external modules with npm, e.g.

npm install classnames --save

Why it should be avoided

Note that any module installed through npm will be included in the bundled output of your component. Therefore, only use an external module if it is absolutly required to prevent bloat in your exported component.

Alternatives

If you are creating a lot of components that absolutly must require say, the classnames package, then you should add classnames as a peer dependency to all of your components and have the parent project that's requiring your module have classnames as a dependancy.