Diff function to compare two objects and return the values for keys that differ

diff.js

import {uniq} from 'lodash';

/**
 * Shallow compare two objects, returning those props that are different with values from `b`.
 * @param {*} a
 * @param {*} b
 */
const diff = (a, b) => {
  if (a === b) {
    return {};
  }

  if ((a && !b) || (b && !a)) {
    return b;
  } else if (!a && !b) {
    return {};
  }

  const difference = {};
  const keys = uniq(Object.keys(a), Object.keys(b));
  keys.forEach(key => {
    if (b[key] !== a[key]) {
      difference[key] = b[key];
    }
  });
  return difference;
};

export default diff;