JavaScript - TypeScript: XMLHttpRequest

Como utilizar XMLHttpRequest para realizar solicitudes con JavaScript.

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
    </head>
    <body>
        <button id="boton" onclick="boton()">BOTON</button>

        <script>
            function reqListener() {
            console.log(this.responseText);
            }

            function boton(){
                const req = new XMLHttpRequest();
                req.addEventListener("load", reqListener);
                req.open("GET", "http://127.0.0.1:8080");
                req.send();
            }
        </script>
    </body>
</html>