看了一天也看不出问他，求大神解？？？？
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
var txt11 = parseInt(document.getElementById('txt1').value);
var txt22 = parseInt(document.getElementById('txt2').value);
var select1 = document.getElementById('select').value;
var result= '';
switch(select1)
{
case '+':
result=txt11 + txt22;
break;
case '-';
result=txt11 - txt22;
break;
case '*':
result=txt11 * txt22;
break;
case '/';
result=txt11 / txt22;
break;
}
document.getElementById('fruit').value=result;
}
</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>
