为啥不行唉唉唉
<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
var one=document.getElementById("txt1").value;
var two=document.getElementById("txt2").value;
var three=document.getElementById("select").value;
var C;
}
switch (three)
{
case "+":
C = parseInt(one)+parseInt(two);
break;
}
document.getElementById("fruit").value=C;
</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>
