isObject = a => {
  if (typeof a === 'object') {
    return true;
  }
  return false;
};

function serialize(o, target = {}, prefix = '') {
  Object.keys(o).forEach(key => {
    const value = o[key];
    if (isObject(value)) {
      serialize(value, target, prefix + key + '.');
    } else {
      target[prefix + key] = value;
    }
  });

  return target;
}

function deserialize(src, target = {}) {
  Object.keys(src).forEach(key => {
    const objPath = key.split('.');
    const propName = objPath.splice(objPath.length - 1)[0];
    const o = objPath.reduce((acc, pName) => acc[pName] = acc[pName] || {}, target);
    o[propName] = src[key];
  });
  return target;
}

o1 = {
  title: 'title',
  banner: {
    title: 'asd'
  },
  validations: {
     req: '',
     minmax:''
  },
  placeholders:{
     firstName: ''
  }
};


deserialize(serialize(o1))