// config.js
const config = require('rc')('setupios', {
  default: 'value',
  other: {
     thing: 'blah'
  }
});

module.exports = config;
// index.js
'use strict';

const cfg = require('./config');

console.log(cfg);

which allows overriding the config via ENV and CLI as well:

node index.js --default foo --other.value ok

and

setupios_default=foo setupios_thing__blah=blah2 node index.js