Sederhana script

<form name="myform" action="javascript.php" onsubmit="return validasi()" method="post">
First name    :<input type="text" name="fname">
Last name    :<input type="text" name="lname">
umur        :<input type="text" name="age">
<input type="submit" nama="ok" value="submit">
</form>

<script language="javascript" type="text/javascript">
function validasi() {

    var x = document.forms["myform"]["fname"].value;
    var vlname = document.forms["myform"]["lname"].value;
    var usia = document.forms["myform"]["age"].value;
   
    if (x == null||x =="") {
        alert("nama depan harus diisi");
        return false;
    }
    if (vlname == null||vlname =="") {
        alert("nama belakang harus diisi");
        return false;
    }
    if (usia == null||usia =="") {
        alert("nama depan harus diisi");
        return false;
    }
   
}
</script>