I am making an app and right now I am coding the backend with express js in node js. For some reason, It is saying that the username and password is invalid.

Backend testing

app.get("/signUp", async (req, res) => {
const json = req.body;
const user = await UserModel.findOne(json["username"])
if(!json["username"] || json["username"] === "" || !json["password"] || json["password"] === "") {
    return res.status(400).send({
        "status": 400,
        "message": "Username and/or password is empty. New user was not created"
    })
}
else if(user.type != null) {
    return res.status(409).send({
        "status": 409,
        "message": "User already exists with given username. New user was not created."
    })
}
else {
    await UserModel.create({
        username: json["username"],
        password: json["password"] 
    })
    return res.status(200).send({
        "status": 200,
        "message": "New user was created."
    })
}

})