动态获取列表框中的内容

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT=""><script language="javascript">
function showS1() {
document.getElementById('s1').style.visibility = "visible";
} function setText() {
document.getElementById('text1').value = document.getElementById('s1').value;
}
</script>
</HEAD><BODY>
<INPUT TYPE="text" NAME="text1" onclick="showS1();" >
<BR>
<SELECT NAME="s1" onChange="setText()" style="visibility:hidden">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</SELECT>
</BODY>
</HTML>