How to implement partial automatic refresh of table information obtained from the interface-PHP Chinese Network Q&A

html如下：

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>title</title>

<script language="javascript" src="../JS/login.js"></script>
<link rel="stylesheet" href="../CSS/login.css" type="text/css">
</head>
<body onload="Login();">
<div class="main">

  <div id="myDiv" class="table1box">


   <table id="table1" class="table1" border="1px">
    <tr>
     <th>信息</th>
     <th>msg</th>
     <th>认证码</th>
    </tr>
    </div>
    </div>
   </table>


</body>
</html>

js如下：

function Login() {
var xmlhttp;
if (window.XMLHttpRequest) {
xmlhttp = new XMLHttpRequest();
} else {
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}

xmlhttp.onreadystatechange = function() {
  if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
   var datastr = xmlhttp.responseText;
   var dataobj = JSON.parse(datastr)
   let dataarr = [];
   for (let i in dataobj) {
    dataarr.push(dataobj[i]);
   }

   var table = document.getElementById("table1");
   var row = table.insertRow(table.rows.length);
   var c1 = row.insertCell(0);
   c1.innerHTML = dataarr[0];
   var c2 = row.insertCell(1);
   c2.innerHTML = dataarr[1];
   var c3 = row.insertCell(2);
   c3.innerHTML = dataarr[2];
  }
}
xmlhttp.open("POST", "https://api.123321yun.com/api/user/login?username=test123&password=123456", true);
xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xmlhttp.send();

}

小白求帮忙