求大神帮忙看看，为什么显示不了结果
<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
var txt1=parselnt(document.getElementById('txt1').value);
var txt2=parselnt(document.getElementById('txt2').value);
var select = document.getElementById("select").value;
var result;
switch(select){
case'+':
result = txt1+txt2;
break;
case '-':
result = txt1-txt2;
break;
case '*':
result = txt1*txt2;
break;
case'/':
result=txt1/txt2;
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>
