javascript 键盘输入过滤，只能输入数字，小数一位且只能输入5

$("#right_div2 input[type=‘text‘][class=‘textClass‘][id^=‘asd_‘]").live("keydown",function(event) {
                var desValue = $(this).val()+event.char;
                if(event.keyCode>31 && event.keyCode != 128)
                {
                    if(!/(^(\d+)$)|(^(\d+\.)$)|(^(\d+\.[05])$)/.test(desValue))
                    {
                        event.preventDefault();
                    }
                }
            });