Responsive YouTube or Vimeo vids from http://toddmotto.com/fluid-and-responsive-youtube-and-vimeo-videos-with-fluidvids-js/

JavaScript: responsive iframes

(function() {
    var iframes = document.getElementsByTagName('iframe');
    
    for (var i = 0; i < iframes.length; i++) {
        var iframe = iframes[i];
        var players = /www.youtube.com|player.vimeo.com/;
        if(iframe.src.search(players) !== -1) {
            var videoRatio = (iframe.height / iframe.width) * 100;
            
            iframe.style.position = 'absolute';
            iframe.style.top = '0';
            iframe.style.left = '0';
            iframe.width = '100%';
            iframe.height = '100%';
            
            var div = document.createElement('div');
            div.className = 'video-wrap';
            div.style.width = '100%';
            div.style.position = 'relative';
            div.style.paddingTop = videoRatio + '%';
            
            var parentNode = iframe.parentNode;
            parentNode.insertBefore(div, iframe);
            div.appendChild(iframe);
        }
    }
})();