<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
//获取第一个输入框的值
var txt1 = parseInt(document.getElementById('txt1').value);
//获取第二个输入框的值
var txt2 = parseInt(document.getElementById('txt2').value);
//获取选择框的值
var selectSymbol = document.getElementById('select').value;
//设置一个作用结果的空值
var result = 0;
//获取通过下拉框来选择的值来改变加减乘除
switch(selectSymbol){
case "+":return result = txt1 + txt2;break;
case "-":return result = txt1 - txt2;break;
case "*":return result = txt1 * txt2;break;
case "/":return result = txt1 / txt2;break;
}
//设置结果输入框的值
document.getElementById('fruit').velue = result;
}
</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' onclick='count()' value=' = ' /> <!--通过 = 按钮来调用创建的函数，得到结果-->
<input type='text' id='fruit' />
</body>
</html>
