title: iframe src add autoplay=true parameter onclick with existing value
body: <pre><code>&lt;iframe id="iframe" src="//player.net/14965165444001/default_default/index.html?videoId=4784345556001" allowfullscreen webkitallowfullscreen mozallowfullscreen&gt;&lt;/iframe&gt;
  
  &lt;button&gt;click&lt;/button&gt;
  </code></pre>
  
  <p>On iframe src, when clicked the "button".. it have to add "?autoplay=true" with the present src value.</p>
  
  <p>Like this I add 5 elements inside the slider.</p>