求指教，看不出来自己的问题在哪啊啊啊啊
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>switch</title>
<input type="text" id="a"></input>
<input type="button"value="选择工作模式" onclick="b()"></input>
<script type="text/JavaScript">
function b(){
var myweek=document.getElementById("a").value;
switch(myweek)
{
case 1:
case 2:
document.write("学习理念知识");
break;
case 3:
case 4:
document.write("到企业实践");
break;
case 5:
document.write("总结经验");
break;
case 6:
case 7:
document.write("周六、日休息和娱乐");
break;
default;
}}
</script>
</head>
<body>
</body>
</html>
