40个请求后xmlhttp-readystate = 0

Question

这是我的代码，我想上传8000个用户，在上传到@serever/userup.php 40次后，它因readystate = 0错误而失败

var xhttp;
   sendReq(i);

   function sendReq(i)
   {
      var cellcount = columns.length;

      xhttp = new XMLHttpRequest();

        //console.log(jsondata[i][columns[1]]);



        xhttp.onreadystatechange = function() {
          if (this.readyState == 4 && this.status == 200) {
            //console.log(this.responseText);
            console.log('sent '+i);

                if (i<rowcount) 
                { 
                    i++;
                    sendReq(i)
                }         
          }
          else
          {
            console.log('error');
          }
        };
        xhttp.open("POST", "https://server/userup.php", true);
        xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
        xhttp.send("region="+loggedRegion+"&campname="+camptitle+"&campid="+cid+"&custcode="+jsondata[i][columns[0]]+"&custname="+jsondata[i][columns[1]]+"&custmob="+jsondata[i][columns[2]]+"&custnation="+jsondata[i][columns[3]]+"&custarea="+jsondata[i][columns[4]]); 
}

是否有任何解决方案等待，直到readystate更改为4并继续上传？