注意:Option中的O是要大写的，不然语法报错 
1.动态创建select 
      function createSelect(){ 
var mySelect = document.createElement_x("select");
          mySelect.id = "mySelect";  
          document.body.appendChild(mySelect);
      } 
2.添加选项option 
     function addOption(){ 
          //根据id查找对象，
           var obj=document.getElementByIdx_x(‘mySelect‘); 
           //添加一个选项
obj.add(new Option("文本","值"));    //这个只能在IE中有效
         obj.options.add(new Option("text","value")); //这个兼容IE与firefox
     } 
3.删除所有选项option 
     function removeAll(){
           var obj=document.getElementByIdx_x(‘mySelect‘);
obj.options.length=0; 
     } 
4.删除一个选项option 
function removeOne(){
           var obj=document.getElementByIdx_x(‘mySelect‘); 
           //index,要删除选项的序号，这里取当前选中选项的序号 
var index=obj.selectedIndex;
obj.options.remove(index);
     } 
5.获得选项option的值 
var obj=document.getElementByIdx_x(‘mySelect‘); 
var index=obj.selectedIndex; //序号，取当前选中选项的序号 
var val = obj.options[index].value; 
6.获得选项option的文本 
var obj=document.getElementByIdx_x(‘mySelect‘); 
var index=obj.selectedIndex; //序号，取当前选中选项的序号 
var val = obj.options[index].text; 
7.修改选项option 
var obj=document.getElementByIdx_x(‘mySelect‘); 
var index=obj.selectedIndex; //序号，取当前选中选项的序号 
var val = obj.options[index]=new Option("新文本","新值"); 
8.删除select 
      function removeSelect(){
            var mySelect = document.getElementByIdx_x("mySelect");
mySelect.parentNode.removeChild(mySelect);
     } 

javaScript操作select