<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
var all;
var count1=document.getElementById("txt1").value;
var count2=document.getElementById("txt2").value;
var sele=document.getElementById("select").value;
switch(sele)
{case "+": all=parseInt(count1)+parseInt(count2); break;
case "-": all=parseInt(count1)-parseInt(count2); break;
case "*": all=parseInt(count1)*parseInt(count2); break;
default : all=parseInt(count1)/parseInt(count2);
}
document.getElementById("fruit").value=all;
}
</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=' = ' /> <!--通过 = 按钮来调用创建的函数，得到结果-->
<input type='text' id='fruit' />
</body>
</html>
问题找到了 ，忘记调用函数了。。