NextJS Display API message on the page

I have a login form. The user types their username/password into the form and submits it. The form uses fetch() to send a request to the backend API and get a response back.

I'd like to display a message from the API on the page. It'll be {apiErrorMessage}

For example, the user's account could be locked. The Password could be wrong. The email address could not be confirmed yet.

In the old days I would do this using Partial Page updates AJAX using C# Razor pages. This is a NextJS project and have no idea how to do this.

Should I be using Server Side Rendering? Should I be using Client Side Rendering? UseEffect() hook?

I'd still like the page to look good for SEO purposes.

I'm thinking maybe we have to use a second page to do this with SSR? LoginResult page or something?

Any Help Appreciated :) Thanks!

const Login = () => {

    let apiErrorMessage = "";

    const loginFormSubmit = async (event) => {

    event.preventDefault()

    // Get data from the form.
    const data = {
      username: event.target.username.value,
      password: event.target.password.value,
    }

    const JSONdata = JSON.stringify(data)

    const response = await fetch(`/api/login`)

    const result = await response.json()

    if (response.ok){
        router.push('/dashboard');
    }
    else {
        // Get the error message from API
        apiErrorMessage = result.message;
    }
}


return (
        <div>
            <form onSubmit={loginFormSubmit}>
                <div className="mb-4">
                    <label htmlFor="username"><b>Username</b></label>
                    <input type="text" id="username" required/>
                </div>
                <div className="mb-4">
                    <label htmlFor="password"><b>Password</b></label>
                    <input type="password" id="password" required/>
                </div>
                <button type="submit">Login</button>
            </form>
        </div>
        <div>
            <p>{apiErrorMessage}</p>
        </div>
 )
}

export default Login;

you don't need to create a page for that you can create a simple useState hook :

const [errorMsg,setErrorMsg] = useState('');

when the user fails to login :

else {
   // Get the error message from API
   setErrorMsg(result.message)
}

Now under your <form> you create a <div> that will be only shown when errorMsg !== '' :

{errorMsg === '' ? '' : (<div>
   <p>login failed : ${errorMsg}</p>
</div>)}

as simple as that.