Js Object Diff

object_diff.js

import * as _ from 'lodash';
function objectDiff(prev, now){
  // sanity checks, prev and now must be an object.
  if ( ! _.isObject(prev) || ! _.isObject(now) ){
    return new TypeError("Arguments must both be objects",__filename);
  }

  var changes = {};
  for (var prop in now) {
    // if property is new in now i.e unknown, add it too changes
    if (!prev || !prev.hasOwnProperty(prop) ) {
      changes[prop] = now[prop];
      continue;
    }
    // if the property has another type or value (different object or literal)
    if (prev[prop] !== now[prop]) {

      if ( _.isArray(now[prop]) ) {
         // add the new array if not equal or continue on to next iteration 
        if(!_.isEqual(prev[prop], now[prop] ) ){
          changes[prop] = now[prop];
        }else { 
          continue;
        }
      } else if (_.isObject( now[prop] ) ) {
        // the property is an object, so recurse into ourselves with this key
        var c = objectDiff(prev[prop], now[prop]);
        if (! _.isEmpty(c) )
          changes[prop] = c;
      } else {
        // now[prop] has different primitive value, i.e bool string number
        changes[prop] = now[prop];
      }
    }
  }
  // returns empty object if nothing changed
  return changes;
}