Demo ajax trong javascript Live code

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Ajax javascript toidicode.com</title>
    <script>
        var sendajax = function () {
            //Khoi tao doi tuong
            var xhttp = new XMLHttpRequest() || ActiveXObject();
            //Bat su kien thay doi trang thai cuar request
            xhttp.onreadystatechange = function () {
                //Kiem tra neu nhu da gui request thanh cong
                if (this.readyState == 4 && this.status == 200) {
                    //In ra data nhan duoc
                    addData(this.responseText)
                }
            }
            //cau hinh request
            xhttp.open('GET','description.php?data=true',true);
            //gui request
            xhttp.send();
        }
        var addData = function (data) {
            document.getElementById('result').innerText = data;
        }
    </script>
</head>
<body>
    <p>Click vào button để xem két quả</p>
    <button type="button" onclick="sendajax()">Click</button>
    <p id="result" style="font-size: 25px;color: orange"></p>
</body>
</html>