我的 React 脚本中有这个 onSubmit，当我单击提交按钮时，它会被调用：

const handleSubmit = (event) => {
event.preventDefault();
const form = event.target;
const rawdata = new FormData(form);
const data = {
    email: rawdata.get('email'),
    password: rawdata.get('password'),
};

console.log(data);
const response = fetch('http://localhost:4000/register', {
    method: 'POST',
    headers: {
        'Content-Type': 'application/json',
    },
    body: JSON.stringify(data),
}).then(response => {
    if(response.ok) {
        console.log('Form data sent successfully');
    } else {
        console.error('Failed to send form data');
    }
}).catch (error => console.error(error));
}

它应该将数据发送到我的节点js脚本并调用以下函数：

app.post("/register", function (req, res){
    console.log("inside /register");
    console.log("email: " + req.body.email);
    User.register({username: req.body.email}, req.body.password, function(err, user){
        if(err) {
            console.log(err);
            console.log("couldn't register");
            //res.redirect("/signup");
        } else{
            passport.authenticate("local")(req, res, function(){
                console.log("login granted");
            });
        }
    });
});

但它说我尝试记录的数据（req.body.email）未定义。如果有人可以帮助我，我将不胜感激。谢谢