问如果用户单击外部模式(使用Bulma框架)，我如何防止其关闭？

EN

$(".modal-button").click(function() {
  var target = $(this).data("target");
  $("html").addClass("is-clipped");
  $(target).addClass("is-active");
});

$(".modal-close").click(function() {
  $("html").removeClass("is-clipped");
  $(this).parent().removeClass("is-active");
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/font-awesome/4.6.3/css/font-awesome.min.css" rel="stylesheet">
<link href="https://cdnjs.cloudflare.com/ajax/libs/bulma/0.4.1/css/bulma.css" rel="stylesheet">

<!-- modal button -->
<p>
  <a class="button is-primary is-large modal-button" data-target="#modal">Launch example modal</a>
</p>

<!-- modal content -->
<div id="modal" class="modal">
  <div class="modal-background"></div>
  <div class="modal-content">
    <div class="box">
      <article class="media">
        <div class="media-left">
          <figure class="image is-64x64">
            <img src="http://bulma.io/images/placeholders/128x128.png" alt="Image">
          </figure>
        </div>
        <div class="media-content">
          <div class="content">
            <p>
              <strong>John Smith</strong> <small>@johnsmith</small> <small>31m</small>
              <br> Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aenean efficitur sit amet massa fringilla egestas. Nullam condimentum luctus turpis.
            </p>
          </div>
          <nav class="level">
            <div class="level-left">
              <a class="level-item">
                <span class="icon is-small"><i class="fa fa-reply"></i></span>
              </a>
              <a class="level-item">
                <span class="icon is-small"><i class="fa fa-retweet"></i></span>
              </a>
              <a class="level-item">
                <span class="icon is-small"><i class="fa fa-heart"></i></span>
              </a>
            </div>
          </nav>
        </div>
      </article>
    </div>
  </div>
  <button class="modal-close"></button>
</div>

  var modal = document.getElementById('modal');
  var elements = document.getElementsByClassName('toggle-modal');
  for (var i = 0; i < elements.length; i++) {
    elements[i].addEventListener('click', toggleClass);
  }

  function toggleClass() {
    modal.classList.toggle('is-active');
  }

<link href="https://cdnjs.cloudflare.com/ajax/libs/bulma/0.4.1/css/bulma.css" rel="stylesheet"/>
  
  
  <button class="toggle-modal">Open Modal</button>
  <div class="modal" id="modal">
    <div class="modal-background"></div>
    <div class="modal-card">
      <header class="modal-card-head">
        <p class="modal-card-title">Modal title</p>
        <button class="delete toggle-modal"></button>
      </header>
      <section class="modal-card-body">
        <!-- Content ... -->
      </section>
      <footer class="modal-card-foot">
        <a class="button is-success toggle-modal">Save changes</a>
        <a class="button toggle-modal">Cancel</a>
      </footer>
    </div>
  </div>