我的代码哪里有错，同学们帮我找找吧
<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
var var1=document.getElementById("txt1").value;
var var2=document.getElementById("txt2").value;
var sign=document.getElementById("select").value;
var fruit;
switch(sign)
{
+:fruit=parseInt(var1)+parseInt(var2);break;
-:fruit=parseInt(var1)-parseInt(var2);break;
*:fruit=parseInt(var1)*parseInt(var2);break;
/:fruit=parseInt(var1)/parseInt(var2);break;
}
document.getElementById("fruit").value=fruit;
}
</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()"/>
<input type='text' id='fruit'/>
</body>
</html>
