title: Accordion - close one item when opening another one
body: <p>I want to automatically close one item when another one is open, so there is just one open at any one time.</p>
  
  <p><strong>HTML</strong></p>
  
  <pre><code>&lt;ons-list-item tappable class="accordion" onclick="fn.toggle(this)"&gt;List 1&lt;/ons-list-item&gt;
    &lt;div class="panel"&gt;
      &lt;ons-list-item tappable&gt;Item 1&lt;/ons-list-item&gt;
      &lt;ons-list-item tappable&gt;Item 2&lt;/ons-list-item&gt;
    &lt;/div&gt;
  </code></pre>
  
  <p><strong>JS</strong></p>
  
  <pre><code>window.fn = {};
  window.fn.toggle = function(el) {
      el.classList.toggle("active");
      el.nextElementSibling.classList.toggle("show");
  }
  </code></pre>