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 = docu