<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title> 事件 </title>
<script type="text/javascript">
function count(){
var a=parselnt(document.getElementById("txt1").value);
var b=parselnt(document.getElementById("txt2").value);
var c=document.getElementById("select").value;
var d="";
switch(c){
case"+":
d=a+b;
break;
case"-":
d=a-b;
break;
case"*":
d=a*b;
break;
default:
d=a/b;
document.getElementById(fruit).value=d;
}
</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>
