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<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>计算器</title>
<style>
.box{
width:500px;
height: 200px;
background-color: #efefef;
border: 1px solid lightgrey;
text-align: center;
margin: 20px auto;
color: #636363;
border-radius: 15px;
box-shadow: 2px 2px 2px #999;
}
table{
margin: auto;
}
td{
width: 100px;
height: 30px;
padding: 5px 10px;
}
input,select{
width: 100%;
height:100%;
border: none;
text-align: left;
padding-left: 15px;
}
button {
width: 100%;
height: 100%;
border: none;
background-color: skyblue;
color: white;
}
button:hover {
cursor: pointer;
background-color: coral;
width: 110%;
height: 110%;
}
</style>
</head>
<body>
<div class="box">
<h2>计算器</h2>
<form action="">
<table>
<tr>
<td>
<input type="text" name="opt1" palceholder="操作数1">
</td>
<td>
<select name="option" id="">
<option value="null">请选择操作</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="操作数2">
</td>
<td>
<button type="button">计算</button>
</td>
</tr>
<tr>
<td align="right" colspan="2"><h3>结果:</h3></td>
<td align="left" colspan="2"><h3 id="result"></h3></td>
</tr>
</table>
</form>
</div>
<script>
//1.获取操作数,按钮,结果占位符
let opt1 = ducument.getElementById('opt1')[0];
let opt2 = ducument.getElementById('opt2')[0];
let opt = ducument.getElementById('option')[0];
let btn = ducument.getElementById('button')[0];
let result = ducument.getElementById('result');\
//2.给按钮添加事件,进行计算
btn.onclick=function(){
//操作数初始化
let data1=0;
let data2=0;
if (opt1.value.length===0){
alert('第一个操作数不能为空');
opt1.focus();
return false;
}else if (isNaN(opt1.value)){
alert('第一个操作数必须是数字');
opt1.focus();
return false;
}else if (opt2.value.length===0){
alert('第二个操作数不能为空');
opt1.focus();
return false;
}else if (isNaN(opt1.value)) {
alert('第一个操作数必须是数字');
opt1.focus();
return false;
}else{
data1=parseFloat(opt1.value);
data2=parseFloat(opt2.value);
}
//对操作符进行处理
let option = opt.value;//拿到了用户选择的操作
let temp=0;
let flag='';
switch(option){
case 'null':
alert('请选择操作类型');
opt.focus();
return false;
case 'add':
flag='+';
temp=data1+data2;
break;
case 'sub':
flag='-';
temp=data1-data2;
break;
case 'mul':
flag='*';
temp=data1*data2;
break;
case 'div':
flag='/';
//进行除数不能为零的判断和处理
if(data2==0){
alert('除数不能为零');
opt2.focus();
opt2.value='';
return false;
}else{
temp=data1/data2;
//四舍五入,保留两位小数
temp=Math.round(temp*100)/100
}
break;
}
let str='<span style="color:coral">';
str+=data1 + '' +flag+ '' +data2+ '='+temp;
str+='</span>';
result.innerHTML=str;
}
</script>
</body>
</html>点击 "运行实例" 按钮查看在线实例
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