title: Property 'params' does not exist on type 'Event'
body: <p>I'm trying to get the selected value from the click-event using <code>select2</code> and <code>TypeScript (2.1)</code>. I followed the example <a href="https://select2.github.io/examples.html#events" rel="nofollow noreferrer">here</a>:</p>
  
  <p>However, in <code>TypeScript</code> I always get the following error:</p>
  
  <blockquote>
    <p>Symbol 'params' cannot be properly resolved, probably it is located in inaccessible module</p>
  </blockquote>
  
  <p>when trying to access <code>evt.params</code>.</p>
  
  <p>My function:</p>
  
  <pre><code>// bind to the select-event
  $theElement.on("select2:select", (evt: Event) =&gt; {
      if (!evt) {
          var args = "{}";
      } else {
          var args = JSON.stringify(evt.params, function (key, value) { // &lt;-- here is the error
              if (value &amp;&amp; value.nodeName) return "[DOM node]";
              if (value instanceof $.Event) return "[$.Event]";
              return value;
          });
      }
  });
  </code></pre>
  
  <p>I checked the <code>Event</code>'s source a.k.a. lib.d.ts located in <code>C:\Program Files (x86)\Microsoft SDKs\TypeScript\2.1</code> and indeed, there is no <code>params</code> defined.</p>
  
  <p>So, how can I access the property without changing the type to <code>any</code>?</p>
  
  <p>Here is a screenshot from Chrome's <code>Developer Tools</code>:</p>
  
  <p><a href="https://i.stack.imgur.com/CMcdd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/CMcdd.png" alt="enter image description here"></a></p>