this version will run with npm start, but when attempting to run the built version behind nginx, it appears to have issues
is-path-cwd 
Check if a path is the current working directory
Install
$ npm install is-path-cwd
Usage
const isPathCwd = require('is-path-cwd');
isPathCwd(process.cwd());
//=> true
isPathCwd('unicorn');
//=> false
License
MIT © Sindre Sorhus