bootstrap

function getExam() {
var selectNianji = document.getElementById("nianji").value;
var selectXueqi = document.getElementById("xueqi").value;
if(selectNianji == "选择年级" || selectNianji == null) {
alert("请选择年级");
}
if(selectXueqi == "选择学期" || selectXueqi == null) {
alert("请选择学期");
}
var xmlHttp = null;
try {
xmlHttp = new XMLHttpRequest();
} catch(e) {
try {
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
} catch(e) {
alert("您的浏览器不支持该操作，推荐您使用最新的谷歌浏览器！");
return;
}
}
var url = "http://<%=request.getServerName()%>:<%=request.getLocalPort()%><%=this.getServletContext().getContextPath()%>/SelectServlet?type=selectKaoShiXinXi&schoolid=11e7-34a4-0c05154b-9ba7-1906c1801458&nianji="+selectNianji+"&xueqi="+selectXueqi;
xmlHttp.open("GET", url, false);
xmlHttp.send(null);
var str = xmlHttp.responseText;
var obj = eval('(' + str + ')');

var optionString = "<option >选择考试</option>";  //定义html内容
$("#exam").find('option').remove();
for(var i = 0; i < obj.length; i++){
var ob = obj[i];
var bname = ob.name;
var bdate = ob.date;
                          optionString += "<option value='"+ bdate +"' name='"+ bname +"'>" + bname + "</option>";                               //动态添加
}
                if (selectExam.options.length == 0){
                    $("#exam").html(optionString);//添加
                    $("#exam").selectpicker('refresh');//刷新
                }
}