InterfaceTextBoxandButtonAlert

<!DOCTYPE html>
<html>
<head>
    <title>Davitra Eka S XI RPL 2</title>
</head>
<body>
    <p id="coba"></p>
    <input type="text" name="nilai" id="nilai">
    <input type="button" id="btnAmbilNilai" value="Ambil Nilai" onclick="ambilNilai();">

    <script type="text/javascript">
        function ambilNilai()
        {
            var objNilai = document.getElementById("nilai")[0];
            var n = objNilai.value;
            alert("Nilainya adalah " + n);
        }
    </script>
</body>
</html>