在MongoDB上插入数据后，它表明我无法阅读属性＆＃x27; _id＆＃x27;不确定的

Question

服务器端代码

在这里您可以看到这是我的服务器端代码，在下面，我已将客户端代码以及显示什么错误。而且我无法抓住这里的问题

app.post("/service", async (res, req) => {
          const newService = req.body;
          const result = await databaseCollection.insertOne(newService);
          res.send(result);
        });

客户端代码

fetch("http://localhost:5000/service", {
      method: "POST", // or 'PUT'
      headers: {
        "Content-Type": "application/json",
      },
      body: JSON.stringify(data),
    })
      .then((response) => response.json())
      .then((result) => {
        console.log("Success:", result);
      })
      .catch((error) => {
        console.error("Error:", error);
      });
  };

错误是

(node:5388) UnhandledPromiseRejectionWarning: TypeError: Cannot read property '_id' of undefined
    at E:\htmll\Assignment_11\Server\myapp\node_modules\mongodb\lib\operations\common_functions.js:64:17
    at Array.map (<anonymous>)
    at prepareDocs (E:\htmll\Assignment_11\Server\myapp\node_modules\mongodb\lib\operations\common_functions.js:63:17)
    at new InsertOneOperation (E:\htmll\Assignment_11\Server\myapp\node_modules\mongodb\lib\operations\insert.js:42:74)
    at Collection.insertOne (E:\htmll\Assignment_11\Server\myapp\node_modules\mongodb\lib\collection.js:149:64)
    at E:\htmll\Assignment_11\Server\myapp\index.js:37:47
    at Layer.handle [as handle_request] (E:\htmll\Assignment_11\Server\myapp\node_modules\express\lib\router\layer.js:95:5)
    at next (E:\htmll\Assignment_11\Server\myapp\node_modules\express\lib\router\route.js:144:13)
    at Route.dispatch (E:\htmll\Assignment_11\Server\myapp\node_modules\express\lib\router\route.js:114:3)
    at Layer.handle [as handle_request] (E:\htmll\Assignment_11\Server\myapp\node_modules\express\lib\router\layer.js:95:5)
(node:5388) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 2)

Answer 1

您可以使用保存方法而不是Insertone首先添加新的DataBaseCollection（Newservice）首先实例化对象。
在那

之后

您的代码应该看起来像这样：

app.post("/service", async (res, req) => {
    const newService = req.body;
    try {
        const service= await new databaseCollection(newService);
        const savedService=await service.save()
        res.status(200).json(savedService);
    } catch (err) {
        res.status(500).json(err);
    }
});

Answer 2

app.post("/service", async (res, req) => {
  const result  = await new databaseCollection(newService)
  await result.save()
  res.send(result);
});

尝试此方法。