How to execute onsubmit method, after setting the html in body.innerHTML asynchronously

I fetched a login form asynchronously, and setted it inside body. I declared it’s on submit form before that, and now getting a Reference error. Is there any way to set onsubmit using html, without having to call loginForm.onsubmit = login.

const result = await fetch('/session');

if (result) {
    const login = await result.text();
    document.body.innerHTML = login;
}

function login(e) {
    e.preventDefault();
    const loginForm = document.getElementById('loginForm');
    console.log(loginForm);
    const options = { method: loginForm.method, body: new FormData(loginForm) };
    const loginButton = document.getElementById('loginButton');
    const loginButtonHTML = loginButton.innerHTML;
    loginButton.innerHTML = 'Loading...';
    disableElements(loginForm);
    // const result = await fetch(loginForm.action, options);
}

The html is:

<form id="loginForm" action="/user/login" method="post" onsubmit="login">
    <input type="text" name="username" autocomplete="username" placeholder="Username">
    <input type="password" name="password" autocomplete="current-password" placeholder="Password">
    <button id="loginButton" type="submit">Login</button>
</form>