Javascript 为什么我的网站需要重新加载才能正常工作

我的express.js服务器有问题。 我用端口3000在本地托管我的网页

在我的网站上，我有一个用于注册/登录用户的功能。启动服务器后，URL如下所示：http://localhost:3000/ 如果我的URL看起来像这样，并且我尝试注册/登录，我的网站只会重新加载

注册/登录失败并重新加载后，URL将更改为以下内容：http://localhost:3000/?# 当URL看起来像这样时，注册/登录工作非常正常

我的注册函数如下所示：

async function onRegisterSubmit() {
obj = {
    username: document.getElementById("username").value,
    email: document.getElementById("email").value,
    password: document.getElementById("password").value
}
if (validation(obj)) {
    return;
}

const body = JSON.stringify(obj);
const res = await fetch("/register", {
    method: "POST",
    headers: {
        "Accept": "application/json",
        "Content-Type": "application/json"
    },
    body: body
});

if (res.status === 201) {
    alert("Registered succesfully.");
    closeForm();
} else {
    alert("There was an error.");
}}

app.post('/register', function (req, res) {  
if ( !req.body.email 
  || !req.body.password
  || !req.body.username 
  || typeof req.body.email !== 'string' 
  || typeof req.body.password !== 'string'
  || typeof req.body.username !== 'string'
) {
  res.sendStatus(400);
}
users.push({ email: req.body.email, passwordDerivative: encrypt(req.body.password), username: req.body.username });
lists.push({ username: req.body.username, lists: []})

res.status(201).send('Registered user with mail: ' + req.body.email);})

我的express.js/register如下所示：

async function onRegisterSubmit() {
obj = {
    username: document.getElementById("username").value,
    email: document.getElementById("email").value,
    password: document.getElementById("password").value
}
if (validation(obj)) {
    return;
}

const body = JSON.stringify(obj);
const res = await fetch("/register", {
    method: "POST",
    headers: {
        "Accept": "application/json",
        "Content-Type": "application/json"
    },
    body: body
});

if (res.status === 201) {
    alert("Registered succesfully.");
    closeForm();
} else {
    alert("There was an error.");
}}

app.post('/register', function (req, res) {  
if ( !req.body.email 
  || !req.body.password
  || !req.body.username 
  || typeof req.body.email !== 'string' 
  || typeof req.body.password !== 'string'
  || typeof req.body.username !== 'string'
) {
  res.sendStatus(400);
}
users.push({ email: req.body.email, passwordDerivative: encrypt(req.body.password), username: req.body.username });
lists.push({ username: req.body.username, lists: []})

res.status(201).send('Registered user with mail: ' + req.body.email);})

这里有什么问题？我怎样才能让我的网站正常运行而不必先重新加载它

---

提前感谢。

请在我提供了一些代码的情况下发表评论，如果有帮助，请告诉我。如果你需要别的东西，我可以提供。