gistfile1.js

// Url.js from https://github.com/Mikhus/jsurl

function isiOS() {
  return navigator.userAgent.match(/(iPad|iPhone|iPod)/g) ? true : false;
}

function isSafari() {
  var ua = navigator.userAgent.toLowerCase();
  return (ua.indexOf('safari') !== -1) && ua.indexOf('chrome') === -1;
}

function html5Capable() {
  return isiOS() || isSafari();
}

function isHtml5PlayLink() {
  return /\/play_html5$/.test(window.location.href);
}

if (html5Capable() && !isHtml5PlayLink()) { 
  var url = new Url(window.location.href);
  url.path = url.path.concat("/play_html5")
  alert(url.path);
}