You can through option
Try this with some modifications
<div trbidi="on">
<script type="text/javascript">
function MostrarVideo(idYouTube)
{
var contenedor = document.getElementById('divInnerVideo');
if(idYouTube == '')
{contenedor.innerHTML = '';
} else{
var url = idYouTube;
contenedor.innerHTML = '<iframe width="560" height="315" src="https://www.youtube.com/embed/'+ url +'" frameborder="0" allowfullscreen></iframe>';
}
}
</script>
<select onchange="MostrarVideo(this.value);">
<option selected disabled>please selected </option>
<option value="qycqF1CWcXg">test1</option>
<option value="hniPHaBgvWk">test2</option>
<option value="bOQA33VNo7w">test3</option>
</select>
<div id="divInnerVideo">
</div>
If you want to put a default page placed inside id="divInnerVideo"
example:
<div id="divInnerVideo">
<iframe width="560" height="315" src="https://www.youtube-nocookie.com/embed/pES8SezkV8w?rel=0&showinfo=0" frameborder="0" allowfullscreen></iframe>
</div>