I know ajax is easy to use with jquery, but here I am trying to understand ajax with core javascript, I am sending two values name and age from index.html to indexPhp.php, In console it shows this message  XHR finished loading: POST "http://localhost:8080/delPro/indexPhp.php". but it is not showing any result in div, here is html, js and php script
<html>
<head>    
<link rel="stylesheet" type="text/css" href="style.css"/>
<script src="scripts.js"></script>
</head>        
<body>            
Name: <input type="text" id="name" name="name"><br><br>
Age:  <input type="text" id="age" name="age"><br><br>  
<button type="submit" value="Submit" onclick="showUser()">Submit</button>
<div id="resultDiv"></div>     
</body>        
</html>
Javascript
function showUser() {
var hr = new XMLHttpRequest();
var url= "indexPhp.php";   
var name= document.getElementById("name").value;
var age= document.getElementById("age").value;    
var vars = {Name: name, Age: age};
hr.open("POST",url,true);
hr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
hr.onreadystatechange = function(){
    if(hr.readyState == 4 && hr.status == 200){
        var return_data = hr.responseText;
        alert(hr.responseText);
        document.getElementById("resultDiv").innerHTML = return_data;
    }        
}
  hr.send(vars);
}
php script
if(isset($_POST['name']) && isset($_POST['age'])){
echo  $name = $_POST['name'] . " " . $age = $_POST['age'];    
}
 
    