<select id="test">
<option value="1" selected>1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select><script>
document.getElementById("test").value = "2";
</script>
<option value="1" selected>1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select><script>
document.getElementById("test").value = "2";
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
</head><body>
<select id="test">
<option value="1" selected>1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
<script>
var s1=document.getElementById("test");
var length;
length=s1.length;
for(i=0;i<length;i++)
{
if (s1[i].value == "2")
s1[i].selected = true;
}
</script>
</body>
</html>
<option value="1" selected>1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select><script>
document.getElementById("test").value = "2";
</script>