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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>计算器</title>
</head>
<body>
<style>
.box {
width: 500px;
height: 200px;
background-color: lightblue;
border: 1px solid #efefef;
border-radius: 15px;
box-shadow: 2px 2px 2px #999;
}
</style>
<div class="box">
<table>
<caption>计算器</caption>
<tr>
<td><input type="text" name="opt1" placeholder="第一个操作数"></td>
<td><select name="option" id="">
<option value="null">请选择</option>
<option value="add">+</option>
<option value="sub">-</option>
<option value="mul">*</option>
<option value="div">/</option>
</select></td>
<td><input type="text" name="opt2" placeholder="第二个操作数"></td>
<td><button type="button">计算</button></td>
</tr>
<tr>
<td align="right" colspan="2"><h3>计算结果:</h3></td>
<td align="left" colspan="2"><h3 id="result">15</h3></td>
</tr>
</table>
</div>
<script>
//获取变量
let opt1 = document.getElementsByName('opt1')[0];
let opt2 = document.getElementsByName('opt2')[0];
let opt = document.getElementsByName('option')[0];
let btn = document.getElementsByTagName('button')[0];
let result = document.getElementById('result');
btn.onclick = function (){
let data1 = 0;
let data2 = 0;
if (opt1.value.length === 0) //判断文本框内容长度
{
alert('第一个操作数不能为空');
opt1.focus();
return false;
} else if (isNaN(opt1.value)) //判断文本框内容是否为数字
{
alert('第一个操作数必须为数字');
opt1.focus();
return false;
} else if (opt2.value.length === 0)
{
alert('第二个操作数不能为空');
opt2.focus();
return false;
} else if (isNaN(opt2.value))
{
alert('第二个操作数必须为数字');
opt2.focus();
return false;
} else {
data1 = parseFloat(opt1.value);
data2 = parseFloat(opt2.value);
}
//对操作符进行处理
let option = opt.value;
let tmp = 0;
let flag = '';
switch (option) {
case 'null':
alert('请选择操作符');
opt.focus();
return false;
case 'add' :
flag = '+';
tmp = data1 + data2;
break;
case 'sub':
flag = '-';
tmp = data1 - data2;
break;
case 'mul':
flag = '*';
tmp = data1 * data2;
break;
case 'div':
flag = '/';
if (data2 === 0){
alert('除数不能为0');
opt2.focus();
return false
}
tmp = data1 / data2;
tmp = Math.round(tmp *100) / 100;
break;
}
result.innerHTML = tmp;
}
</script>
</body>
</html>点击 "运行实例" 按钮查看在线实例
