js 操作select和option

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optionfunction 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optionvar 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);     }