* {
margin: 0;
padding: 0;
}
tbody button{
width: 40px;
height: 40px;
border: 0;
background: pink;
text-align: center;
margin-right: 14px;
}
tbody td {
float: left;
}
thead input{
height: 35px;
width: 200px;
}
<div class="box">
<table>
<thead>
<tr>
<td colspan="4"><input type="text" id="input_box"></td>
</tr>
</thead>
<tbody>
<!-- 第一排 -->
<tr>
<td><button class="num" id="7" onclick="jsq(this.id)">7</button></td>
<td><button class="num" id="8" onclick="jsq(this.id)">8</button></td>
<td><button class="num" id="9" onclick="jsq(this.id)">9</button></td>
<td><button id="+" onclick="jsq(this.id)">+</button></td>
</tr>
<!-- 第二排 -->
<tr>
<td><button class="num" id="4" onclick="jsq(this.id)">4</button></td>
<td><button class="num" id="5" onclick="jsq(this.id)">5</button></td>
<td><button class="num" id="6" onclick="jsq(this.id)">6</button></td>
<td><button id="-" onclick="jsq(this.id)">-</button></td>
</tr>
<!-- 第三排 -->
<tr>
<td><button class="num" id="1" onclick="jsq(this.id)">1</button></td>
<td><button class="num" id="2" onclick="jsq(this.id)">2</button></td>
<td><button class="num" id="3" onclick="jsq(this.id)">3</button></td>
<td><button id="*" onclick="jsq(this.id)">*</button></td>
</tr>
<!-- 第四排 -->
<tr>
<td><button class="num" id="0" onclick="jsq(this.id)">0</button></td>
<td><button class="num" onclick="AC()">AC</button></td>
<td><button class="num" id="=" onclick="res()">=</button></td>
<td><button id="/" onclick="jsq(this.id)">/</button></td>
</tr>
</tbody>
</table>
</div>
// 獲取輸入框
var input_box = document.querySelector('#input_box');
// console.log(input_box);
// 獲取輸入的值
var num = document.querySelectorAll('.num');
// 獲取計算器輸入框數字
function jsq(num){
input_box.value += num; // 所有按鈕調用此函數,讓輸入框得到每次點擊獲取值的字符串拼接
}
function res(){
input_box.value = eval(input_box.value); // 最後把拼接的字符串通過eval()系統函數計算結果
}
function AC(){
input_box.value = ' ';
// console.log(5);
}
```