youtube
$('.youtube').each(function() {
var movie = $(this).children('iframe'),
url = movie.attr('src'),
id = url.match(/[\/?=]([a-zA-Z0-9]{11})[&\?]?/)[1];
movie.before('<img src="http://img.youtube.com/vi/'+id+'/sddefault.jpg" />').remove();
$(this).on('click', function() {
$(this).after('<iframe width="640" height="480" src="https://www.youtube.com/embed/'+id+'?rel=0&autoplay=1" frameborder="0" allowfullscreen></iframe>').remove();
});
});
/*<div class="youtube">
<iframe width="640" height="480" src="https://www.youtube.com/embed/動画ID?rel=0&autoplay=1" frameborder="0" allowfullscreen></iframe>
</div>*/