This is a bit of magic I didn't know about.
There is a global object that you can add things to and it becomes available in basically any file in the project.
This becomes handy when I need the root path of project so I can create directories from much deeper down the project.
In app.js I can do the following:
var path = require("path");
global.appRoot = path.resolve(__dirname);
...
In a route, much deeper down, I can then do:
let filePath = appRoot + "/some/file/path";
Frikken weird. It seems to be some sort of window analog that exists in browsers. I also imagine this very poor form as attaching to window is also bad form.