Close Dropdown SubMenus when closing the Dropdown Main

$(document).ready(function(){
  $('.dropdown-submenu a.sub').on("click", function(e){
    $(this).next('ul').toggle();
    e.stopPropagation();
    e.preventDefault();
  });
});

.dropdown-submenu {
    position: relative;
}

.dropdown-submenu .dropdown-menu {
    top: 0;
    left: 100%;
    margin-top: -1px;
}

  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script><scriptsrc="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<div class="container">
  <h2>Multi-Level Dropdowns</h2>
  <p>In this example, we have created a .dropdown-submenu class for multi-level dropdowns (see style section above).</p>
  <p>Note that we have added jQuery to open the multi-level dropdown on click (see script section below).</p>                                        
  <div class="dropdown">
    <button class="btn btn-default dropdown-toggle" type="button" data-toggle="dropdown">Tutorials
    <span class="caret"></span></button>
    <ul class="dropdown-menu">
      <li><a tabindex="-1" href="#">HTML</a></li>
      <li><a tabindex="-1" href="#">CSS</a></li>
      <li class="dropdown-submenu">
        <a class="sub" tabindex="-1" href="#">New dropdown <span class="caret"></span></a>
        <ul class="dropdown-menu">
          <li><a tabindex="-1" href="#">2nd level dropdown</a></li>
          <li><a tabindex="-1" href="#">2nd level dropdown</a></li>
          <li class="dropdown-submenu">
            <a class="sub" href="#">Another dropdown <span class="caret"></span></a>
            <ul class="dropdown-menu">
              <li><a href="#">3rd level dropdown</a></li>
              <li><a href="#">3rd level dropdown</a></li>
            </ul>
          </li>
        </ul>
      </li>
    </ul>
  </div>
</div>