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"));   

   }

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);

   }