After inserting data on mongodb it shows me Cannot read property '_id' of undefined

Question

server-side Code

Here you can see this is my server-side code and it's below i have put my client-side code and what error is showing. And I can't catch what's wrong here

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

Client Side Code

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);
      });
  };

Error Is

(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

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

Try this method.

Answer 2

you can use save method instead of insertOne first instantiate your object by adding new databaseCollection(newService). and after that call save method to insert your collection

Use res.json instead of res.send to enforce Content-Type to be of JSON type

Your code should look like this:

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);
    }
});