- it技术
- 使用JavaScript完成一个简易计算器的功能
使用JavaScript完成一个简易计算器的功能
<!DOCTYPE html
>
<html
>
<head
>
<meta charset
="utf-8" />
<title
>简单的计算器
</title
>
</head
>
<body
>
<input type
="text" id
="num1" placeholder
="请输入一个数字" />
<select id
="operation">
<option value
="+">+</option
>
<option value
="-">-</option
>
<option value
="*">*</option
>
<option value
="/">/</option
>
</select
>
<input type
="text" id
="num2" placeholder
="请输第二个数字" />
<input type
="button" value
="计算" onclick
="result()" /><br
/>
<span id
="res"> </span
><br
/>
<script type
="text/javascript">
function result() {
var num1
= Number(document
.getElementById("num1").value
);
var operation
= document
.getElementById("operation").value
;
var num2
= Number(document
.getElementById("num2").value
);
if (isNaN(num1
) || isNaN(num2
)) {
alert("您输入的数字不正确");
return;
}
if (operation
== "/" && num2
== 0) {
alert("被除数不能为零");
return;
}
var res
= "";
switch (operation
) {
case "+":
res
= num1
+ num2
;
break;
case "-":
res
= num1
- num2
;
break;
case "*":
res
= num1
* num2
;
break;
case "/":
res
= num1
/ num2
;
break;
}
document
.getElementById("res").innerText
= "计算结果 " + res
;
}
</script
>
</body
>
</html
>
