<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
var num1=document.getElementById("txt1").value;
var x=parseInt(num1);
var num2=document.getElementById("txt2").value;
var y=parseInt(num2);
var choose=document.getElementById("select").value;
var num3=document.getElementById("fruit").value;
var z=parseInt(num3);
switch(choose){
case "+":
z=x+y;
return z;
break;
case "-":
z=x-y;
return z;
break;
case "*":
z=x*y;
return z;
break;
case "/":
z=x/y;
return z;
break;
}
}
</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>
