function setSelectOption(objId, targetValue){//objid：下拉列表框的ID；targetValue：當前所選值 var obj = document.getElementById(objId); if(obj){  var options = obj.options;  if(options){   var len = options.length;   for(var i=0;i<len;i++){    if(options[i].value == targetValue){     options[i].defaultSelected = true;     options[i].selected = true;     return true;    }   }  } else {   alert('missing element(s)!');  } } else {  alert('missing element(s)!'); }}

<select>  <option value="1" <%if(sesssionValue==1){%> selected="selected"<%}%>>1:b </option>  <option value="2" <%if(sesssionValue==2){%> selected="selected"<%}%>>2:b </option>  <option value="3" <%if(sesssionValue==3){%> selected="selected"<%}%>>3:c </option>  <option value="4" <%if(sesssionValue==4){%> selected="selected"<%}%>>4:d </option></select>