js获取select标签的值且兼容IE与firefox

jsp代码：

<form id="search">
 <select id="jobSelect" style="width: 200px;" name="jobSelect">
  <s:if test='jobSelect == null || jobSelect == ""'>
   <option selected="selected" value="-1">--依职类筛选--</option>
  </s:if>
  <s:else>
   <option value="-1">--依职类筛选--</option>
  </s:else>
  <s:iterator value="jobCat" status="s">
   <s:if test="jobSelect == catKey">
    <option value="<s:property value="catKey" />" selected="selected">
     <s:property value="catCnName" />
    </option>
   </s:if>
   <s:else>
    <option value="<s:property value="catKey" />">
     <s:property value="catCnName" />
    </option>
   </s:else>
  </s:iterator>
 </select> <br />
 <select id="areaSelect" style="width: 200px;" name="areaSelect">
  <s:if test='areaSelect == null || areaSelect == ""'>
   <option selected="selected" value="-1">--依地区筛选--</option>
  </s:if>
  <s:else>
   <option value="-1">--依地区筛选--</option>
  </s:else>
  <s:iterator value="workAreaCat" status="s">
   <s:if test="areaSelect == areaCat">
    <option value="<s:property value="areaCat" />" selected="selected">
     <s:property value="catCnName" />
    </option>
   </s:if>
   <s:else>
    <option value="<s:property value="areaCat" />">
     <s:property value="catCnName" />
    </option>
   </s:else>
  </s:iterator>
 </select>
 <input class="send2" type="button" onclick="validate();return false" value="查询" />
 <span style="color: red;" mce_style="color: red;" id="requiredParam"></span>
</form>

js代码：

<mce:script type="text/javascript"><!--
 validate = function(){
  var jobSelect;
  var areaSelect;
  var search = document.getElementById("search");
  for(var i=0;i<search.jobSelect.length;i++){
   if(search.jobSelect[i].selected){
    jobSelect = search.jobSelect[i].value;
   }
  }
  for(var i=0;i<search.areaSelect.length;i++){
   if(search.areaSelect[i].selected){
    areaSelect = search.areaSelect[i].value;
   }
  }
  if(jobSelect == -1 && areaSelect == -1){
   document.getElementById('requiredParam').innerHTML = '请设定筛选条件后查询';
   return;
  }
  var param = {
         target : '../Index/JobFrame.action',
         method : 'post',
         form   : 'search',
         div    : 'box'
     }
     var as = new AjaxSender(param);
     as.send()
 }
// --></mce:script