HTML:关于Select中的OPTGROUP使用

      下面这段代码的精髓在于“Clean Select”也就是每次动态构建Select前先要清空用OPTGROUP分组的Select。

 var dropReport = $("dropReport");     
        
        // Clean Select
        var blank = document.createTextNode('');        
        while (dropReport.childNodes.length > 0) { 
            dropReport.replaceChild(blank, dropReport.childNodes[0]); 
            dropReport.removeChild(blank); 
        } 
        
         var opt = new Option("--------请选择报表--------","");
         dropReport.options.add(opt);          
          
          var systemGroup  = document.createElement("OPTGROUP");
          systemGroup.label = 'System';
          dropReport.appendChild(systemGroup);
          for (var item = items.nextNode();item;item = items.nextNode())
          {            
              var REPORT_TYPE = item.selectSingleNode("REPORT_TYPE").nodeTypedValue;
              if (REPORT_TYPE == 'system')
              {              
                    var REPORT_ID= item.selectSingleNode("REPORT_ID").nodeTypedValue;
                    //alert(REPORT_ID);
                    var REPORT_NAME= item.selectSingleNode("REPORT_NAME").nodeTypedValue;
                    //alert(REPORT_NAME);
                    
                    var newOption = document.createElement("OPTION");
     
                    newOption.text=REPORT_NAME;
                    newOption.value=REPORT_ID;
                    dropReport.options.add(newOption);                    
              }
          }