mongodb - 如何从这个查询中隐藏 _id ？

Question

如何从这个查询中隐藏 _id，我使用 express node.js ？

我有这个查询，我创建了一个 API，但我想隐藏 _id。

这是查询：

router.get("/", (req, res) => {
  VerbsDE.find({}, { _id: 0 })
    .limit(1)
    .then(verbs => {
      res.send(verbs);
    });
});

/////////////////////////////////////// /// 这是收藏：

[
      {
        Indicative: {
          Present: [
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            },
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            },
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            }
          ],
          Perfect: [
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            },
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            },
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            }
          ],
          Past: [
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            },
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            },
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            }
          ],
          Pluperfect: [
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            },
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            },
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            }
          ],
          Future_I: [
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            },
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            },
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            }
          ],
          Future_II: [
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            },
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            },
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            }
          ]
        },
        Imperative: {
          Worte: [
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            },
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            },
            {
              _id: "5bb9009249efde355376ad29",
              pron: "xxx",
              verb: "xxx xxx xxx"
            }
          ]
        },
        _id: "5bb9009249efde355376ad23",
        verbName: "abbilden",
        __v: 0
      }
    ];

我试图隐藏 _id ，但每次我出错时，我都想获取数据而不是 Id。

Answer 1

有两种主要方法可以做到这一点：

1. 使用排除直接来自 mongo
2. 对结果使用 .map() 函数

Mongo 排除 与您所做的类似，但您需要正确声明变量，如果集合是动态的（例如每个文档中的“预设”、“过去”等发生变化），这可能会很痛苦。

您需要以嵌套属性的方式使用 fields 选项，只需更改以下内容：

router.get("/", (req, res) => {
  VerbsDE.find({}, { _id: 0 })
    .limit(1)
    .then(verbs => {
      res.send(verbs);
    });
});

到这里：

router.get("/", (req, res) => {
  VerbsDE.find({}, { _id: 0, __v: 0, 'Indicative.Present._id': 0 })
    .limit(1)
    .then(verbs => {
      res.send(verbs);
    });
});

但是，由于文档的 Present、Past 等 分配，这可能需要大量重复。现在让我们试试：

在响应前使用地图

现在你有：

router.get("/", (req, res) => {
      VerbsDE.find({}, { _id: 0, __v: 0 })
        .limit(1)
        .then(verbs => {
          // We'll use map before sending the response
          res.send(verbs);
        });
    });

所以，map函数如下：

function cleanVerbs(verbs) {
    return verbs.map(doc => {
        // For each doc, make a newDoc
        const newDoc = {};
        for (const mood in doc) {
            // mood will be 'Imperative' 'Indicative', etc.
            if (!newDoc[mood]) {
                // If out newDoc object does not have 'Imperative', etc. property, assign it as object.
                newDoc[mood] = {};
            }
            if (mood === 'verbName') {
                // You have verbName as root property, treat it differently
                newDoc[mood] = doc[mood];
                break; // Avoid further execution on this cycle
            }
            for (const time in doc[mood]) {
                console.log('MOOD & TIME: ', [mood, time]);
                const entries = doc[mood][time];
                const newTimeEntries = entries.map(e => {
                    delete e._id;
                    return e;
                });
                // This will set the newTimeEntries for this Mood's time.
                newDoc[mood][time] = newTimeEntries;
            }
        }
        return newDoc;
    });
}

那么新的get 方法将是这样的：

router.get("/", (req, res) => {
      VerbsDE.find({}, { _id: 0, __v: 0 })
        .limit(1)
        .then(verbs => {
          // We'll use map before sending the response
          res.send(cleanVerbs(verbs));
          // Try res.json(cleanVerbs(verbs)) instead :)
        });
    });

只记得在编写此路由时声明cleanVerbs 函数并将其置于作用域（可在同一文件中访问）。

注意： 我强烈建议从以下位置更改 Mongo 集合架构：

你必须做什么：

{
    _id: "5bb9009249efde355376ad23",
    verbName: "abbilden",
    grammar: [
      Indicative: {
            Present: [...],
            Past: [...],
      },...
    ],
    __v: 0
}

将 Moods 保存在每个集合的数组中将简化迭代，例如不对 .map(...) 函数使用 if (mood === 'verbName'){...} 测试

Answer 2

您可以尝试使用投影 (https://docs.mongodb.com/manual/reference/method/db.collection.find/)：

{projection: { _id: 0 }}

如：

router.get("/", (req, res) => {
  VerbsDE.find({}, {projection: { _id: 0 }})
    .limit(1)
    .then(verbs => {
      res.send(verbs);
    });
});