title: amp-form: always trigger page reload on submit on mobile
body: <p>I have a form which displays something depending on the response from server.</p>
  <p>Success response would also display the results of query while error response would display errors and dynamically change css styles to emphasize elements.</p>
  <p>Code works on desktop.</p>
  <p>However in mobile, it always trigger page reload/refresh on submit and would not display elements inside <code>&lt;div submit-error&gt;</code> and <code>&lt;div submit-error&gt;</code>.</p>
  <p>Browsers tested on mobile (always trigger page reload/refresh):</p>
  <ul>
  <li>Safari 14.4.2 mobile</li>
  <li>Chrome 87.0.4280.77</li>
  </ul>
  <p>Here's a simple html code to reproduce:</p>
  <pre><code>&lt;form method=&quot;POST&quot; action-xhr=&quot;/api/some-path&quot; target=&quot;_top&quot;&gt;
  
      &lt;input type=&quot;submit&quot; value=&quot;Submit&quot; /&gt;
  
      &lt;div submit-success&gt;
           &lt;h2&gt;Success&lt;/h2&gt;
      &lt;/div&gt;
  
      &lt;div submit-error&gt;
           &lt;h2&gt;SError&lt;/h2&gt;
      &lt;/div&gt;
  &lt;/form&gt;
  </code></pre>
  <p>Is there any way to prevent this behavior or make it in such a way it behaves like <code>event.preventDefault()</code> on non-amp pages?</p>
  <p>If no, then is the AMP way of submitting forms in mobile always need to reload/redirect to another page?</p>