请问我哪里写得不对？
<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
var tt1=document.getElementById("txt1").value;
var tt2=document.getElementById("txt2").value;
var cou=document.getElementById("select").value;
//var t1=parselnt(txt1), t2=parselnt(txt2);
var result;
switch(cou)
{
case "+":
//result=t1 + t2;
result=parselnt(tt1) + parselnt(tt2);
break;
case "-":
//result=t1 - t2;
result=parselnt(tt1) - parselnt(tt2);
break;
case "*":
//result=t1 * t2;
result=parselnt(tt1) * parselnt(tt2);
break;
case "/":
result=parselnt(tt1) / parselnt(tt2);
//result=t1 / t2;
}
//return result;
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>
