title: Javascript + JsDoc: How to document new ES6 datatypes like map?
body: <p>I'm trying to use JSDoc in my ES6 project, I'm returning a Map:</p>
  
  <pre><code>/**
   * Some documentation.. 
   *
   * @returns {undefined} &lt;- This should be replaced
   */
  function returningMap() {
      const someMap = new Map();
      someMap.set("key", {a, b, c});
      return someMap;
  }
  </code></pre>
  
  <p>How should I document this with <code>@returns</code>?</p>
  
  <p>There is not good answer <a href="http://usejsdoc.org/tags-type.html" rel="noreferrer">here</a>.</p>