Gulp / NPM Dev dependencies - What do I do with them when my site is finished?

Hi

I've started learning Gulp and Webpack and one thing none of the tutorials cover is... when your project is finished and ready to be deployed - what do you do with / what happens to all the dev dependencies?

The node_modules folder itself is huge and I'm assuming you don't upload this to your web server(or maybe you do)? But then does that mean all the benefits you get from using things like SASS/minification are only available on your localhost project, and therefore it's only the finished files that get deployed (which would then mean having to edit minified code etc live on the site if you need to make any small changes).

This part of the learning process is harder to find info about than anything else I've experienced so far in web development. I also think it's poor none of the major learning libraries (Lynda, Treehouse etc) cover this at the end of the tutorials. It's like, congratulations you've now built a site you can upload. OK, but what do I do with the hundreds of files in all of my dependencies etc? Do I upload them normally as part of the site, and if not do how do I prevent this or does npm prevent this automatically?

Any guidance/explanation would be amazing.

Emily