Get OS version

osver.js

function getOSver() {
  var ua = navigator.userAgent;
  var uaindex, userOS, userOSver;

  if(ua.match(/iPad/i) || ua.match(/iPod/i) || ua.match(/iPhone/i)) {
    userOS = "iOS";
    uaindex = ua.indexOf("OS ");
  } else {
    userOS = "unknown";
  }

  if(userOS === "iOS"  &&  uaindex > -1) {
    userOSver = ua.substr(uaindex + 3, 3).replace("_", ".");
  } else {
    userOSver = "unknown";
  }

  return userOSver;
}