有没有办法在javascript中获取当前的用户名和密码？

// 示例：使用JWT进行身份验证
fetch('/login', {
    method: 'POST',
    headers: {
        'Content-Type': 'application/json'
    },
    body: JSON.stringify({
        username: 'exampleUser',
        password: 'examplePassword'
    })
})
.then(response => response.json())
.then(data => {
    localStorage.setItem('token', data.token);
})
.catch(error => console.error('Error:', error));

// 示例：使用OAuth进行身份验证
const authWindow = window.open('https://authprovider.com/oauth/authorize', '_blank');
authWindow.onload = () => {
    const urlParams = new URLSearchParams(authWindow.location.search);
    const token = urlParams.get('access_token');
    localStorage.setItem('token', token);
    authWindow.close();
};