document.addEventListener('DOMContentLoaded', function() { var videoFrame = document.getElementById('videoFrame'); var iframeWindow = videoFrame.contentWindow; videoFrame.onload = function() { var iframeDocument = iframeWindow.document; var video = iframeDocument.getElementById('my-player'); video.addEventListener('play', function() { document.body.classList.add('dimmed'); }); video.addEventListener('pause', function() { document.body.classList.remove('dimmed'); }); }; });