function selPage(){
var currentPage = document.getElementById("selPage").value;
document.getElementById("pageNo").value=currentPage;
document.getElementById("selectForm").submit();
}
<select id="selPage" onchange="selPage()">
<%
for (int i = 1; i <= totalPage; i++) {
%>
<option value="<%=i%>"<%=i == pageNo ? "selected" : ""%> >第<%=i%>页
</option>
<%
}
%>
</select>