你可以在mongo使用$round。
参考此https://www.mongodb.com/docs/manual/reference/operator/aggregation/round/

我用change streamers解决了这个问题。我在对特定集合执行任何插入或更新操作后检查发布数据。如果有一个值与我的长数字十进制模式相匹配，则更新为四舍五入版本。

const FORMAT_NEEDED_DECIMAL_REGEX = /^\d+\.\d{3,}$/;
const DECIMAL_ROUNDING_PLACE = 2;

const config = [[{
  $match: { operationType: { $in: ['insert', 'update'] } },
}], {
  fullDocument: 'updateLookup',
}];

const yourModelStream = YourModel.watch(...config);

yourModelStream.on('change', (postData) => {
  const { documentKey: { _id: id }, updateDescription, operationType, fullDocument } = postData;

  const document = operationType === 'update' ? updateDescription.updatedFields : fullDocument;

  const updateQuery = Object.keys(document).reduce((acc, field) => {
    if (FORMAT_NEEDED_DECIMAL_REGEX.test(document[field])) {
      return { ...acc, [field]: { $round: [`$${field}`, DECIMAL_ROUNDING_PLACE] } };
    }
    return acc;
  }, {});

  if (Object.keys(updateQuery).length) {
    YourModel.updateOne({ _id: id }, [{ $set: updateQuery }]).exec().catch(() => undefined);
  }
});