Is the [[Prototype]] field in my React Axios post response data expected?

I am using axios for post request which is giving me correct response data but with an additional field
[[Prototype]]: Object.

I don’t want this in my apis. By testing with postman, this additional field is not showing. Why Axios is giving me this additional field and how I can get rid of it?

Here is my react code.

 const submitHandler = (event) => {
    event.preventDefault();
    let name = event.target.name.value;
    let head = parseInt(event.target.head.value);
    console.log(name, head);
    const body = {
      name: name,
      flag: 1,
      accountNumber: 100,
      headNo: head,
      sumDebit: 0,
      sumCredit: 0,
    };
    axios
      .post("http://localhost:5000/api/accounts/create", body)
      .then((res)=>{console.log (res.data);})
      .catch((err) => console.log(err));
  };
  

Here is my express code. I am only using these middlewares.

app.use(cors({origin:true,credentials:false}));
app.use(express.json({ extended: true }));
app.use("/api/accounts", account_route);
app.use("/api/transaction", transaction_route);
app.use("/api/account-info", accounts_route);

My Api code is sent in this format.

res.json(reqData);