js处理下拉菜单 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=null;
     }

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);
     }