Get a plain object (without nested keys) based on a multi-level object

flattenObj.js

/*
 * Flattens an object by creating a plain object (without nested keys).
 * The returned object keys are strings with dots for nested source object.
 * Example :
 * flattenObj({ a: 1, b: { c: 2, d: null } }) => { 'a': 1, 'b.c': 2, 'b.d': null }
 */
function flattenObj (obj, prefix, acc) {
  acc = acc || {};
  prefix = prefix || '';
  var separator = '.';

  if (typeof obj === 'object' && obj !== null) {
    for (var key in obj) {
      if (typeof obj[key] === 'object' && obj[key] !== null) {
        flattenObj(obj[key], prefix ? prefix + separator + key : key, acc);
      }
      else {
        acc[prefix ? prefix + separator + key : key] = obj[key];
      }
    }
  }
  return acc;
}


/*
 * Returns a diff between to objects (after flattening them)
 */
function diff (oldObj, newObj) {
  var flattenedOld = flattenObj(oldObj);
  var flattenedNew = flattenObj(newObj);
  var diff = [];
  for (var key in flattenedOld) {
    if (flattenedNew[key] === undefined) {
      diff.push({ 'type': '-', key: key, old: flattenedOld[key], new: null });
    }
    else if (flattenedNew[key] !== flattenedOld[key]) {
      diff.push({ 'type': '~', key: key, old: flattenedOld[key], new: flattenedNew[key] });
    }
  }
  for (var key in flattenedNew) {
    if (flattenedOld[key] === undefined) {
      diff.push({ 'type': '+', key: key, old: null, new: flattenedNew[key] });
    }
  }
  return diff;
}