lodash assign test

assign.js

var _ = require('lodash');

var history = {
  BYZ: {someData: 'original'},
  ABC: {someData: 'originalABC'}
};

var revision = {
  BYZ: {someData: 'revisedBYZ'},
  ABC: {someData: 'revisedABC'},
  CBA: {someData: 'revisdeNOP'}
};

// _.assign(history, revision);
// _.assign(history, revision, function(objVal, sourceVal) {
//   // console.log(objVal, key, object, source);
//   return _.isUndefined(objVal) ? sourceVal : objVal;
// });

_.assign(history, revision, function(objVal, sourceVal, key) {
  // console.log(objVal, key, object, source);
  if(_.isUndefined(objVal)) {
    var newObj = {};
    newObj[key] = sourceVal;
    console.log('EMIT', newObj);
    return sourceVal;
  }
  console.log('HISTORY COLLISION:', key);
  return objVal;
});