A simple method to stop YouTube, Vimeo, and HTML5 videos from playing.

stop-video.js

/**
 * Stop an iframe or HTML5 <video> from playing
 * @param  {Element} element The element that contains the video
 */
    var stopVideo = function ( element ) {
    element.querySelectorAll('iframe').forEach(function(iframe) {
        if ( iframe.contentWindow ) { /* send stop to content */
            stopVideo(iframe.contentWindow.document);
        }
        else { /* Cross Domain, resetting src is all we can do, and the iframe might fail loading same url */
            var iframeSrc = iframe.src;
            iframe.src = iframeSrc;
        }
    });
    element.querySelectorAll('video').forEach(function(item) { item.pause(); });
    element.querySelectorAll('audio').forEach(function(item) { item.pause(); });
    };
    
    
    // then call from top level document
    stopVideo(document);

it won't work with YouTube iframe.contentWindow.document - this won'r pass XSS

To the best of my knowledge, if resetting iframe src does not work(iframe contains autoplay video), there is no way to do this.