Frame content dissapear

<!DOCTYPE HTML>
<html lang="en-US">
<head>
  <meta charset="UTF-8">
  <title></title>
</head>
<body>
  <div id="placeholder"></div>
  <div id="script_placeholder"></div>

  <script type="text/javascript">
    (function(){
      var scriptText = "\
      (function(placeholderId){\
              var placeholder = document.getElementById(placeholderId);\
              placeholder.innerHTML = '<iframe id=\"banner-iframe\"></iframe>';\
              var loader = document.getElementById('banner-iframe').contentDocument;\
              loader.open();\
              loader.write('<h1>What the hack?</h1>');\
              loader.close();\
              alert(1);\
      })('placeholder')"

      var scriptPlaceHolder = document.getElementById('script_placeholder');
      var scriptElement = document.createElement('SCRIPT');
      scriptElement.type = 'text/javascript';
      scriptElement.text = scriptText;
      scriptPlaceHolder.appendChild(scriptElement);
    })();
  </script>

</body>
</html>