index.html

<!DOCTYPE html>
<html lang="en" dir="ltr">
  <head>
    <meta charset="utf-8">
    <title></title>
    <script src='xlsx.full.min.js'></script>
  </head>


  <body>
    <form id="postForm" action='' method="post">
      <p>Select weight of your package:</p>
      <select id='selectWeightElem' >
        <option selected>---</option>
      </select>
      <p>From:</p>
      <select id='selectFromElem' >
        <option selected>---</option>
      </select>
      <p>To:</p>
      <select id='selectWhereElem' >
        <option selected>---</option>
      </select>

      <button type="button" name="button" id='switchButton'>Switch directions</button>
      <hr/>
      <button type="button" name="button" id='submitButton'>Calculate your price</button>
    </form>
    <p id='deliveryPrice'></p>


    <script src="script.js" charset="utf-8"></script>
  </body>
</html>