Handling Form Submissions in a Single Page Application

The issue you're experiencing is a common one in SPAs. When you submit a form using the default HTML form behavior, it causes a full page reload and sends a traditional form submission to the server. This is why you're seeing the raw HTML response instead of having it integrated into your SPA.

To fix this, you need to intercept the form submissions and handle them with JavaScript. Here's how you can modify your code:

1. Prevent Default Form Submission

First, you need to prevent the default form submission behavior:

JAVASCRIPTCopied
document.getElementById('login-form').addEventListener('submit', function(event) {
  event.preventDefault(); // Prevent the form from submitting normally
  
  // Handle the form submission with JavaScript
  handleFormSubmission(this);
});

2. Create a Function to Handle Form Submissions

Create a function that will handle the form data and make AJAX requests:

JAVASCRIPTCopied
function handleFormSubmission(form) {
  const formData = new FormData(form);
  
  fetch(form.action || window.location.href, {
    method: form.method || 'POST',
    body: formData,
    headers: {
      'X-Requested-With': 'XMLHttpRequest' // This helps the server identify AJAX requests
    }
  })
  .then(response => response.text())
  .then(html => {
    // Update your page content with the response
    document.getElementById('app-content').innerHTML = html;
    
    // Update the URL if needed
    const targetUrl = form.getAttribute('data-target-url');
    if (targetUrl) {
      navigateTo(targetUrl);
    }
  })
  .catch(error => {
    console.error('Error submitting form:', error);
  });
}

3. Modify Your HTML Forms

Add a data attribute to your forms to specify where they should navigate after submission:

HTMLCopied
<form id="login-form" method="POST" action="/login" data-target-url="/dashboard">
    <input type="text" name="username" />
    <input type="password" name="password" />
    <button type="submit">Login</button>
</form>

4. Modify Your Backend

You might need to adjust your backend to handle AJAX requests differently. Instead of rendering a full HTML page, you might want to return just the content portion or JSON data:

JAVASCRIPTCopied
// Server-side pseudocode
if (request.headers['X-Requested-With'] === 'XMLHttpRequest') {
  // Return just the content portion for AJAX requests
  return render('content-only.html');
} else {
  // Return the full page for regular requests
  return render('full-page.html');
}

5. Apply This to All Forms

You'll need to apply this pattern to all forms in your application. You can do this individually or use a more general approach:

JAVASCRIPTCopied
// Apply to all forms with a specific class
document.querySelectorAll('form.spa-form').forEach(form => {
  form.addEventListener('submit', function(event) {
    event.preventDefault();
    handleFormSubmission(this);
  });
});

This approach will allow you to handle form submissions within your SPA without causing full page reloads, maintaining the smooth user experience you're aiming for.