overrideDefaultConfig.js

/**
 Examples: 
  overrideDefaultConfig({ a: 1, b: 2 }, { a: 2 }); // => { a: 2, b: 2 }
  overrideDefaultConfig({ a: { b: { c: 2 }}}, { a: { b: { c: 3, d: 4 }}}); // => { a: { b: { c: 3 } } }
  overrideDefaultConfig({ a: 1, b: [2, 3]}, { a: 2, b: [4, 5] }); // => { a: 2, b: [4, 5]}

 * This returns a new copy of the defaults and assigns all existing properties on the settings to the default config.
 * @param {*} inputArg
 * @returns {object}
 */
const overrideDefaultConfig = (defaults, settings) => Object.keys(defaults).reduce((newObject, property) => {
  if(typeof defaults[property] === "object" && !Array.isArray(defaults[property])) {
   newObject[property] = overrideDefaultConfig(defaults[property], settings[property]);
  } else {
   newObject[property] = settings.hasOwnProperty(property) ? settings[property] : defaults[property]; 
  }
  return newObject;
}, {});