如何在jquery中计算下拉菜单的求和值

<select class="dropdown-item">
  <option value="1">1</option>
  <option value="2">2</option>
  <option value="3">3</option>
</select>
<select class="dropdown-item">
  <option value="4">4</option>
  <option value="5">5</option>
  <option value="6">6</option>
</select>
<button id="calculate">计算总和</button>
<div id="result"></div>

$(document).ready(function() {
  $('#calculate').click(function() {
    var sum = 0;
    $('.dropdown-item').each(function() {
      var value = parseInt($(this).val());
      sum += value;
    });
    $('#result').text('总和：' + sum);
  });
});