สอบถามวิธีบวกเลขโดยใช้ jQuery ด้วยครับ (มีตัวอย่าง)

<script type="text/javascript">


$(document).ready(function(e) {
    var setting = {
        width: 150,
        max:130
    };

    function reAbility(){
        lv = parseInt($('#select_lv').val());
        plus =  parseInt($('#select_plus').val());
        $('.ability_player table td, .position_player ul li').each(function(){
            new_val = lv+plus+parseInt($(this).find('input[name="ability_ori"]').val());
            $(this).find('.ability_val').text(new_val);

            pNum = (new_val/setting.max)*100;
            pBar = Math.ceil((pNum/100)*setting.width);
            $(this).find('span.ability_bar').animate({width:pBar+'px'});

            pClass= 'gray';
            if(pNum>20) pClass= 'green';
            if(pNum>40) pClass= 'yellow';
            if(pNum>60) pClass= 'orange';
            if(pNum>80) pClass= 'red';
            $(this).find('.ability_val').removeClass('gray').removeClass('green').removeClass('yellow').removeClass('orange').removeClass('red').addClass(pClass);

        });
    }

    $('#btn_back').click(function(){
        window.location='/db/player/';
    });

    $('#abi_down').click(function(){
        $('#select_lv option').prop('selected',false);
        $('#select_plus option').prop('selected',false);

        $('#select_lv option:first').prop('selected',true);
        $('#select_plus option:first').prop('selected',true);
        reAbility();
    });

    $('#abi_up').click(function(){
        $('#select_lv option').prop('selected',false);
        $('#select_plus option').prop('selected',false);

        $('#select_lv option:last').prop('selected',true);
        $('#select_plus option:last').prop('selected',true);
        reAbility();
    });

    $("#select_lv, #select_plus").live('change',reAbility);

    reAbility();

});
</script><!-- content -->