jQuery val() didnt working, this is the simple script:

$("#com_form").submit(function() {
            var name = $("#nama").val();
                            var komentar = $("#komentar").val();
            alert.("Hi, "+name+" this is your comment: "+komentar)
            });

        });*/

this is the HTML form:

<form method="post" name="com_form" id="com_form">
  <p>What is your name:<br>

    <input type="text" name="nama" id="nama">
  </p>
  <p>Leave your comment here:<br>

    <input type="text" name="komentar" id="komentar">
  </p>
  <p>
    <input type="submit" name="button2" id="button2" value="Submit">
  </p>
</form>

actually, I was tried to create ajax post, the value "nama" is submited but not "komentar". So I tried to debug using alert (like one above) and still "komentar" is not change. What should I do?