value sent to controller by using JS

I'm new to codiginiter and it's still developing.

I'm trying to send a JS value to codiginiter controller but I'm getting errors. Firebug says syntax error. But when I correct it, another syntax error is being shown.

I think the problem is with my script. Can anyone can figure out what's wrong? All I want is to send username value to method in controller. Following alert is triggered when I press the button (tested and working).

<script type="text/javascript">   
    $(function(){
        $("#postAnswer").click(function(){  // passing down the event 
            alert("checked");
            $.post('<?php echo base_url(); ?>homepage/postanswer', {
                //username:document.getElementById('username').value
                username:<?php  $ques[0]->username ?> 
            });
        });
    });
</script>