Server-Side Internet Programming - Ajax Script

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>AJAX</title>
    <script>
        function ajax1() {
            var xhttp = new XMLHttpRequest();
            xhttp.onreadystatechange = function() {
                if(this.readyState == 4 && this.status == 200)
                    document.getElementById("res").innerHTML = this.responseText;
            }
            xhttp.open("GET", "ajax1.txt", true);
            xhttp.send();
        }
        function ajax2() {
            var xhttp = new XMLHttpRequest();
            xhttp.onreadystatechange = function() {
                if(this.readyState == 4 && this.status == 200)
                    document.getElementById("res").innerHTML = this.responseText;
            }
            xhttp.open("GET", "ajax2.txt", true);
            xhttp.send();
        }
    </script>
</head>
<body>
    .A.J.A.X.
    <div style="font: size 48">
        <label onmouseover="ajax1()"> A </label>
        <label onmouseover="ajax2()"> B </label>
    </div>
    <div id="res"></div>
</body>
</html>