<!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 num1 = parseInt(document.getElementById("txt1").value);
//获取第二个输入框的值
var num2 = parseInt(document.getElementById("txt2").value)
//获取选择框的值
var select = 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=0;
switch(select){
case '+':
sum = (num1+num2);
break;
case '-':
sum = (num1-num2);
break;
case '*':
sum = (num1*num2);
break;
case '/':
sum = (num1/num2);
break;
default:
sum = 0;
break;
}
document.getElementById("fruit").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="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" value="" />
</body>
</html>
我这个错误非常致命
var select = document.getElementById("select").value;
var select = document.getElementById.("select").value;
这句话，大家来找茬，就因为这句话费了半个下午
document.getElementtById这个地方多了个点