Ajax返回值写入HTML里?

     function showTime(){
          var xhr=new XMLHttpRequest();
          xhr.open("POST","test2.php","true");
          xhr.setRequestHeader("Content-type","application/x-www-form-urlencoded");
          xhr.onreadystatechange=function(){
            if (xhr.readyState==4 && xhr.status==200){
            xhr.responseText;
          }}
          xhr.send();
          setTimeout("showTime()", 3000);
        };
sc.get([ ]).status('unavailable');

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