deepMerge.js

const isObject = (value) => value && typeof value === 'object' && !Array.isArray(value);

const deepMerge = (a, b) => {
  const result = { ...a };
  Object.keys(b).forEach((key) => {
    if (isObject(a[key]) && isObject(b[key])) {
      result[key] = deepMerge(a[key], b[key]);
    } else {
      result[key] = b[key];
    }
  });
  return result;
};