<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style type="text/css">
input {
width: 500px;
height: 70px;
font-size: 45px;
border: none;
}
tr {
text-align: center;
font-size: 40px;
color: blue;
}
td:hover {
cursor: pointer;
background: skyblue;
}
</style>
</head>
<body>
<div id="" align="center">
<input type="" name="" value="0" disabled="disabled" id="showNum" />
<table border="1" cellspacing="0" height="600px" width="500px">
<tr>
<td id="clear">C</td>
<td id="del">退格</td>
<td>%</td>
<td class="ope">/</td>
</tr>
<tr>
<td class="num">7</td>
<td class="num">8</td>
<td class="num">9</td>
<td class="ope">*</td>
</tr>
<tr>
<td class="num">4</td>
<td class="num">5</td>
<td class="num">6</td>
<td class="ope">-</td>
</tr>
<tr>
<td class="num">1</td>
<td class="num">2</td>
<td class="num">3</td>
<td class="ope">+</td>
</tr>
<tr>
<td colspan="2" class="num">0</td>
<td class="num">.</td>
<td id="result">=</td>
</tr>
</table>
</div>
</body>
</html>
<script type="text/javascript">
//1.把数字和小数点归为一类 class="num"
//2.把运算符归为一类 class=opr
//3.等号，归零 退格 显示框 单独添加id
//4.把所有要用的DOM对象获取出来
//做运算：简单的运算，1+2=3 我们得定义三个变量 来保存这个三个数据 第一个数 第二个数 运算符
var numValue1 = '';
var numValue2 = '';
var operator = '';
var showNum = document.getElementById("showNum");
var clear = document.getElementById("clear");
var del = document.getElementById("del");
var result = document.getElementById("result");
//把所有的数字获取出来
var nums = document.getElementsByClassName("num");
//给所有的数字添加点击事件
for (var i = 0; i < nums.length; i++) {
nums[i].onclick = function() {
//判断用户是否在点击小数点
if (this.innerText == '.') {
if (numValue1.indexOf(".") == -1 && numValue1.length >= 1) {
//没有小数点
//获取用户点击的数字
numValue1 += this.innerText;
//把用户点击的数字展示出来
showNum.value = numValue1;
} else {
//
}
} else {
//nums[i].innerText
//showNum.value+=this.innerText;
//获取用户点击的数字
numValue1 += this.innerText;
//把用户点击的数字展示出来
showNum.value = numValue1;
}
}
}
//当用户点击了 运算符之后，把第一个数给第二个数，把第一个数清空，用来接收第二个数字
//获取所有的运算符，绑定点击事件
var opes = document.getElementsByClassName("ope");
for (var i = 0; i < opes.length; i++) {
opes[i].onclick = function() {
//判断用户可能点=或四则
if (numValue2 == '') {
//alert(this.innerText);
//保存用户点击的运算符
//operator = this.innerText;
//把第一个数给第二个数
numValue2 = numValue1;
//把第一个数清空，用来接收下一次用户的输入
numValue1 = '';
} else {
//点=和或四则
//operator = this.innerText;
if (numValue1 != '') {
funResult();
}
}
//保存用户点击的运算符
operator = this.innerText;
}
}
//归零
clear.onclick = function() {
numValue1 = '';
numValue2 = '';
operator = '';
showNum.value = '0';
}
//退格
del.onclick = function() {
if (numValue1.length > 1) {
numValue1 = numValue1.substring(0, numValue1.length - 1);
showNum.value = numValue1;
} else if (numValue1.length == 1) {
numValue1 = '';
showNum.value = '0';
}
}
//给等号绑定点击事件
result.onclick = function() {
//进行运算
if (numValue2 != '') {
funResult();
}
}
// numValue1='0'; numValue2='0';
function funResult() {
//转换类型
var one = Number(numValue2);
var two = Number(numValue1);
var r = 0;
switch (operator) {
case '+':
r = one + two;
break
case '-':
r = one - two;
break
case '*':
r = one * two;
break
case '/':
if (two == 0) {
alert("除数不能为0");
numValue1 = '';
numValue2 = '';
operator = '';
r = 0;
} else {
r = one / two;
}
break
}
//把上一次的结果算出来，赋值给numValue2
numValue2 = r;
把第一个数清空，用来接收下一次用户的输入
numValue1 = '';
showNum.value = numValue2.toFixed(5) * 1; //可以去掉无效的0
}
</script>
效果如图：