funcion2

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=<device-width>, initial-scale=1.0">
    <title>Probando JavaScript</title>
    <style>
        table,th,td {
            border: 1px solid black;
            border-collapse: collapse;
        }
    </style>
</head>
<body>

    <table>
        <thead>
            <tr>
                <td>Tabla del 2</td>
            </tr>
        </thead>
        <tbody>
            <tr>
                <td id="2x0"></td>
            </tr>
            <tr>
                <td id="2x1"></td>
            </tr>
            <tr>
                <td id="2x2"></td>
            </tr>
            <tr>
                <td id="2x3"></td>
            </tr>
            <tr>
                <td id="2x4"></td>
            </tr>
            <tr>
                <td id="2x5"></td>
            </tr>
            <tr>
                <td id="2x6"></td>
            </tr>
            <tr>
                <td id="2x7"></td>
            </tr>
            <tr>
                <td id="2x8"></td>
            </tr>
            <tr>
                <td id="2x9"></td>
            </tr>
            <tr>
                <td id="2x10"></td>
            </tr>
        </tbody>
    </table>



    <script>
        // Desarrollar un script que muestre la tabla del 2 en forma vertical
        // Tabla del 2:
        // 2 x 0 = 0
        // 2 x 1 = 2
        // ....
        // 2 x 9 = 18
        // 2 x 10 = 20

        var celda = ""

        for (var i=0; i<11; i++){
            celda = "2x" + i;
            document.getElementById(celda).innerHTML = producto(i);
        }

        function producto(a){
            return "2 x " + a + " = " + 2*a ;
        }

    </script>

</body>
</html>