Flatten Object

flatten.js

/**
 * Takes a deeply nested object, `source`, and returns an object with
 * dot-separated paths pointing to all primitive values from `source`.
 *
 * Examples:
 *
 *   flatten({ foo: { bar: 1 } })
 *     //=> { 'foo.bar': 1 }
 *
 *   flatten({ foo: [{ bar: 1 }, { bar: 2 }] })
 *     //=> { 'foo.0.bar': 1, 'foo.1.bar': 2 }
 */
function flatten(obj, parent, res = {}){
  for(let key in obj){
    let propName = parent ? parent + '.' + key : key;
    if(typeof obj[key] === 'object' && obj[key] === null){
      flatten(obj[key], propName, res);
    } else {
      res[propName] = obj[key];
    }
  }
  return res;
}