和很多份对了又对，还是找不到错误，就是运行不出来，求大神，在线等
<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
var sum="";
var fir=document.getElementById("txt1").value;
var sec=document.getElementById("txt2").value;
var x=document.getElementById("select").value;
switch(x)
{
case "+":
sum = parseFloat(fir) + parseFloat(sec);
break;
case "-":
sum = parseFloat(fir) - parseFloat(sec);
break;
case "*":
sum = parseFloat(fir) * parseFloat(sec);
break;
default:
sum = parseFloat(fir) / parseFloat(sec);
}
document.getElementById("fruit").value=sum;
}
</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>
