jQuery实现监听下拉框选中内容发生改变操作示例

<script>    $(document).ready(function(){      var defaultId = "${defaultSelected}";      var defaultTime = "${timeName}";      $("select option").each(function(){        if($(this).val()==defaultId || $(this).val()==defaultTime){          $(this).attr("selected","selected");        }      });      $("#all").change(function(){        //alert(document.getElementById("allItem").selected);        if(document.getElementById("allItem").selected == true){          $("#timeText").hide();          $("#timeSelect").hide();        }else{          $("#timeText").show();          $("#timeSelect").show();        }      });    });</script>

<form action="${baseUrl}/report/issueStatus.shtml">  <span>Select a project:</span>  <select name="selectedProId" id="all">    <c:forEach items="${projectNameId}" var="pi">      <option value="${pi.value}">${pi.key}</option>    </c:forEach>    <option value="-1" id="allItem">All</option>  </select>  <span id="timeText">Select a time horizon:</span>  <select name="timeHorizon" id="timeSelect">    <option value="Week">Last week</option>    <option value="Month">Last month</option>  </select>  <button type="submit" id="submit">search</button></form>