/** 
 * Converts an object or array to an 1 dimensional object
 *  with dot delimited key paths as keys
 *
 * @param {(Object|Array)} oldObject
 * @returns {Object} 
 */
const flat = oldObject => {
  // This scope is just to create the new object, to avoid mutating state 
  const newObj = {};
  return flatten(oldObject);
  
  /**
   * Flatten the object
   *
   * @param {(Object|Array)} object
   * @param {string[]} [keys=[]]
   */
  function flatten(object, keys = []) {
    // Can iterate over arrays or objects
    for (let key in object) {
      const value = object[key];
      // Can iterate over arrays or objects
      if (typeof value === 'object') {
        // Optimistically assume `key` is a sane type like string
        // You could do a skip instead:
        //   (typeof key !== 'string') continue
        // Or, coerce to string (must handle null)
        flatten(value, [...keys, key]);
      } else {
        // You could have an options argument to `flat` with delimiter
        // And key transform function like the `flat` npm module
        newObj[keys.concat([key]).join('.')] = value;
      }
    }
    return newObj;
  }
};

// Examples:
// const o = {
//   a: {
//     b: [
//       {
//         c: 1
//       },
//       {
//         d: {
//          e: 100
//         }
//       }
//     ]
//   }
// }
// 
// flat(o);
// #=> { 'a.b.0.c': 1, 'a.b.1.d.e': 100 }