操作select option

1.动态创建select

      function createSelect(){

       var mySelect = document.createElement("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.getElementById('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.getElementById('mySelect');
  
        obj.options.length=0;  

     }

4.删除一个选项option

function removeOne(){
           var obj=document.getElementById('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.getElementById('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.getElementById('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.getElementById('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.getElementById("mySelect");
        mySelect.parentNode.removeChild(mySelect);
     }