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老师批语：
编程 : 使用js完成一个功能相对完整的计算器案例
div {
width: 500px;
height: 200px;
background-color: lightblue;
border: 1px solid grey;
text-align: center;
margin: auto;
color: black;
border-radius: 15px;
box-shadow: 2px 2px 2px #999999;
}
table {
margin: auto;
}
td {
width: 100px;
height: 30px;
padding: 6px 6px;
}
input {
width: 100%;
height: 80%;
border: none;
text-align: left;
margin-left: 15px;
}
select {
width: 100%;
margin-left: 12px;
}
button {
width: 80%;
height: 100%;
border: none;
background-color: lightcoral;
color: white;
margin-left: 5px;
}
button:hover {
cursor: pointer;
color: #000;
background-color: coral;
width: 90%;
height: 110%;
}<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<link rel="stylesheet" href="style.css">
<title>计算器实例</title>
</head>
<body>
<div>
<h2>简易计算器</h2>
<form>
<table>
<tr>
<td>
<input type="text" name="sz1" placeholder="第一个数值">
</td>
<td>
<select name="xz" 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="sz2" placeholder="第二个数值">
</td>
<td>
<button type="button" name="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>
let sz1 = document .getElementsByName('sz1')[0];
let xz = document .getElementsByName('xz')[0];
let sz2 = document .getElementsByName('sz2')[0];
let but = document .getElementsByName('button')[0];
let result = document .getElementById('result');
but.onclick = function () {
let data1 = 0;
let data2 = 0;
if (sz1.value.length === 0) {
alert('第一个数值不能为空');
sz1.focus();
return false;
} else if (isNaN(sz1.value)) {
alert('第一个数值必须为数字');
sz1.focus();
return false;
} else if (sz2.value.length === 0) {
alert('第二个数值不能为空');
sz2.focus();
return false;
} else if (isNaN(sz2.value)) {
alert('第二个数值必须为数字');
sz2.focus();
return false;
}else{
data1 = parseFloat(sz1.value);
data2 = parseFloat(sz2.value);
}
let xz1 = xz.value;
let temp = 0;
let flag = '';
switch(xz1){
case 'null':
alert('请选择运算符');
xz1.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 = '/';
if (data2 === 0){
alert('除数不能为零');
sz2.focus();
xz1.value = '';
return false;
}else {
temp = data1 / data2;
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
总结 : 最后的result的输出结果 , 还需要研究一下!!!
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