ios设备中angularjs无法改变页面title的解决方法

$rootScope.$watch('title',function(title){
 var body = document.getElementsByTagName('body')[0];
 document.title = title;
 var iframe = document.createElement("iframe");
 iframe.title = '';
 iframe.width = 0;
 iframe.height = 0;
 iframe.setAttribute("src", "/empty.png");

 iframe.addEventListener('load', function() {
 setTimeout(function() {
  iframe.removeEventListener('load');
  document.body.removeChild(iframe);
 }, 0);
 });
 document.body.appendChild(iframe);
});