使用Node Js Mongoose时防止重复数据进入MongoDB数据库

const userSchema = new mongoose.Schema({
  email: { type: String, unique: true },
  // 其他字段...
});

const User = mongoose.model('User', userSchema);

userSchema.pre('save', function(next) {
  const self = this;
  User.findOne({ email: self.email }, function(err, user) {
    if (err) {
      return next(err);
    }
    if (user) {
      const error = new Error('Email address already exists.');
      return next(error);
    }
    next();
  });
});

const session = await mongoose.startSession();
session.startTransaction();

try {
  // 执行多个操作，例如插入数据、更新数据等

  await session.commitTransaction();
  session.endSession();
} catch (error) {
  await session.abortTransaction();
  session.endSession();
  throw error;
}