这个代码为啥不灵呢，好奇怪，是哪错了，望高手指导，谢谢！
<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
var x=document.getElementById("txt1").value;
var y=document.getElementById("txt2").value;
var sel=document.getElementById("select").value;
var fur=0;
switch(sel)
{case"+";
fur=parseInt(x)+parseInt(y);
break;
case"-";
fur=parseInt(x)-parseInt(y);
break;
case="*";
fur=parseInt(x)*parseInt(y);
break;
case="/";
fur=parseInt(x)/parseInt(y);
break;
}
document.getElementById("fruit").value =fur;
}
</script>
</head>
<body>
<input type='text' id='txt1' />
<select id='select'>
<option value='+'>+</option>
<option value="-">-</option>
<option value="*">*</option>
<option value="/">/</option>
</select>
<input type='text' id='txt2' />
<input type='button' value=' = ' onclick="count()" /> <!--通过 = 按钮来调用创建的函数，得到结果-->
<input type='text' id='fruit' />
</body>
</html>
