Page not updating when clicking submit
<p>I have HTML and JavaScript code, which must, after clicking submit, change the page. The problem is, when I click the submit button, the page remains the same.</p>

<p>Thanks for the help.</p>

<p>HTML:</p>

<pre><code>&lt;html&gt;
  &lt;head&gt;
    &lt;title&gt;MyApp&lt;/title&gt;
    &lt;meta charset="utf-8"&gt;
    &lt;meta name="viewport" content="width=device-width, initial-scale=1"&gt;
  &lt;/head&gt;
  &lt;body&gt;
    &lt;form id="cart" action="/page" method="POST"&gt;
      &lt;div id="navigation"&gt;Select ID:
        &lt;select id="state" type="text"&gt;
          &lt;option value&gt;-select-&lt;/option&gt;
          &lt;option value="1"&gt;1&lt;/option&gt;
          &lt;option value="2"&gt;2&lt;/option&gt;
          &lt;option value="3"&gt;3&lt;/option&gt;
        &lt;/select&gt;
      &lt;/div&gt;
    &lt;/form&gt;
    &lt;div&gt;           
      &lt;input type="submit" value="submit" id="submit"&gt;
    &lt;/div&gt;
    &lt;script src="script.js"&gt;&lt;/script&gt;
  &lt;/body&gt;
&lt;/html&gt;
</code></pre>

<p>JavaScript:</p>

<pre><code>function() {
  "use strict";
  var state = document.getElementById('state');
  document.addEventListener('DOMContentLoaded', function() {
    document.getElementById('cart').addEventListener('submit', estimateTotal);
    var btnEstimate = document.getElementById('submit');
    btnEstimate.disabled = true;
    state.addEventListener('change', function() {

      if (state.value === '') {
        btnEstimate.disabled = true;
      } else {
        btnEstimate.disabled = false;
      }
    });
  });

  function estimateTotal(event) {
    event.preventDefault();
    if (state.value === '') {
      alert('Please choose your shipping state.');
      state.focus();
    }
  }
})();
</code></pre>