在loopback nodejs中，在保存检查之前，输入具有相同用户in的月份

module.exports = function(UserActivity) {
  UserActivity.observe('before save', async function(ctx, next) {
    if (ctx.instance && ctx.isNewInstance) { // 只在创建新实例时检查
      const { userId, date } = ctx.instance;
      const startOfMonth = new Date(date.getFullYear(), date.getMonth(), 1);
      const endOfMonth = new Date(date.getFullYear(), date.getMonth() + 1, 0);

      const existingRecords = await UserActivity.find({
        where: {
          userId: userId,
          date: { between: [startOfMonth, endOfMonth] }
        }
      });

      if (existingRecords.length > 0) {
        throw new Error('A record for this user in the same month already exists.');
      }
    }
    next();
  });
};