单机按钮票数加一，用total.innerHTML = parseInt(total.innerHTML) + 1可以，但要是用var num = total.innerHTML 把total.innerHTML 都替换掉就不行，为什么

<script>

        function vote(e){

            var total = document.getElementById("total");

            var num = total.innerHTML;

            num = parseInt(num)+1;         //这样就没效果

        }

</script>