JSFiddle - React, Tailwind, and code Playground

HTML

<div id="vidcontainer">
<object width="560" height="315"><param name="movie" value="http://www.youtube.com/v/Ni3ZRedt-dg?version=3&amp;hl=en_GB&amp;rel=0"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/Ni3ZRedt-dg?version=3&amp;hl=en_GB&amp;rel=0" type="application/x-shockwave-flash" width="560" height="315" allowscriptaccess="always" allowfullscreen="true"></embed></object>
</div>

CSS

#vidcontainer{width:100%; height:100%;}

JavaScript

$(document).ready(function(){
    function videoresize(){
        $("object, embed, .format-video iframe").each(function() {
            var orig = $(this);
            var ratio = orig.attr("height") / orig.attr("width");
            var parWidth = orig.parents().find("div:last").width();
            if(orig.attr("width")!=parWidth) {
                orig
                    .attr("width", parWidth)
                    .attr("height", (parWidth * ratio));
            }
        });
    }
    videoresize();
    window.addEventListener('resize', videoresize, false);
});