点击事件就都没了
<!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 sum1 = document.getElementById("txt1").value;
document.write("sum1是："+ sum1):
//获取第二个输入框的值
var sum2 = document.getElementById("txt2").value;
//获取选择框的值
var aa = document.getElementById("select").value;
//获取通过下拉框来选择的值来改变加减乘除的运算法则
var sum;
switch(aa){
case '+':
sum = sum1 + sum2;
break;
case '-':
sum = sum1 - sum2;
break;
case '*':
sum = sum1 * sum2;
break;
default:
sum = sum1/sum2;
break;
}
//设置结果输入框的值
document.getElementById("truit").value = sum;
}
</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='tx2' />
<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>
