1 <input type="button" id="btn" value="按钮"/>
2 <select name="select" id="select">
3 <option value="1">aa</option>
4 <option value="a">bb</option>
5 <option value="c">cc</option>
6 </select>
7 <script type="text/javascript">
8 //点击按钮，让第二项选中
9 document.getElementById(‘btn‘).onclick=function(){
10 document.getElementById(‘select‘).value="a";
11 }
12 </script>
