Travis CI is a popular continuous integration server. It offers handy integration with GitHub, which makes it quick and easy to add to your project.

Travis is configured via .travis.yml. Inside, we're going to declare just two things. We're going to declare that the language that we're working with is node_js and then we can add a list of versions. I'm just going to check version six, but I could have add other lines here to have it check version five, version four, and so on.

language: node_js
- "10"

And that's all it takes to configure Travis for our continuous integration server (when we're working with GitHub).