title: LitElement equivalent of React "key" concept
body: <pre><code>&lt;example name="One"&gt;&lt;/example&gt;
  &lt;example name="Two"&gt;&lt;/example&gt;
  &lt;example name="Three"&gt;&lt;/example&gt;
  </code></pre>
  
  <p>Next render looks like this:</p>
  
  <pre><code>&lt;example name="Four"&gt;&lt;/example&gt;
  &lt;example name="Three"&gt;&lt;/example&gt;
  </code></pre>
  
  <p>LitElement will remove the last element and update the first two with new properties.</p>
  
  <p>How do I change this so that LitElement removes all elements except <code>name="three"</code> and a new element is created with <code>name="Four"</code> on first position?</p>
  
  <p>Using React, this would be accomplished by giving them a key property. I want to achieve the same result using LitElement.</p>
  
  <pre><code>&lt;example key="1" name="One"&gt;&lt;/example&gt;
  &lt;example key="2" name="Two"&gt;&lt;/example&gt;
  &lt;example key="3" name="Three"&gt;&lt;/example&gt;
  </code></pre>