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使用js完成一个功能相对完整的计算器案例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>计算器</title>
<style>
.box{
width: 400px;
height: 250px;
background-color: #A6C8FF;
border: 1px solid lightgrey;
text-align: center;
margin: 20px auto;
color: #28a4c9;
border-radius: 10px;
box-shadow: 3px 3px 3px #9999CC;
}
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: #5cb85c;
color: white;
}
button:hover{
cursor: pointer;
background-color: #33CCFF;
width: 110%;
height: 110%;
}
</style>
</head>
<body>
<div class="box">
<h3>计算器</h3>
<form>
<table>
<tr>
<td><input type="text" name="opt1" placeholder="输入框1"></td>
<td>
<select name="option" id="">
<option value="null">请填入数字</option>
<option value="add">+</option>
<option value="sub">-</option>
<option value="mul">*</option>
<option value="div">/</option>
</select>
</td>
</tr>
<tr>
<td><input type="text" name="opt2" placeholder="输入框2"></td>
<td><button type="button">计算</button></td>
</tr>
<tr>
<td align="right"><h3>结果：</h3></td>
<td align="left"><h3 id="result"></h3></td>
</tr>
</table>
</form>
</div>
</body>
</html>
<script>
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 ){
result.innerHTML = '第一个操作不能为空';
opt1.focus();
return false;
}else if (isNaN(opt1.value)){
result.innerHTML = '第一个操作必须为数字';
opt1.focus();
return false;
} else if (opt2.value.length ===0){
result.innerHTML = '第二个操作数不能为空';
opt2.focus();
return false;
}else if (isNaN(opt2.value)){
result.innerHTML = '第二个操作数必须为数字';
opt2.focus();
return false;
} else {
data1 = parseFloat(opt1.value);
data2 = parseFloat(opt2.value);
}
let option = opt.value;
let temp = 0;
let flag = '';
switch (option) {
case 'null':
result.innerHTML = '请选择操作类型';
opt1.focus();
case 'add':
flag = '+';
temp = data1 + data2;
break;
case 'sub':
flag = '-';
temp = data1 - data2;
break;
case 'mul':
flag = '*';
temp = data1 * data2;
break;
case 'div':
flag = '/';
if (data2===0){
result.innerHTML = '除数不能为零';
opt2.focus();
opt2.value = '';
return false;
}else {
temp = data1/data2;
temp = Math.round(temp *100) / 100;
}
break;
}
let str = '<span style="color: #2979ff">'
str += data1 + ' ' +flag+' '+data2+ ' = ' + temp;
str += '</span>';
result.innerHTML = str;
}
</script>点击 "运行实例" 按钮查看在线实例
总结，学完php，学js，感觉没那么难！
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