括号功能未实现，后续更
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>计算器</title>
<style>
body,p,input,ul,li,div{
margin: 0;
padding: 0;
}
#calc{
position: relative;
border-radius: 10px;
margin: 0 auto;
400px;
height: 500px;
background: #ccc;
}
p{
text-align: center;
}
.f-text{
padding-top: 10px;
box-sizing: border-box;
border: 0;
margin: 0 auto;
font-size: 30px;
text-align: right;
400px;
height: 60px;
}
ul{
list-style-type: none;
}
ul li{
float: left;
90px;
height: 50px;
margin: 25px 10px 0 0;
font-size: 30px;
font-family: Arial, Helvetica, sans-serif;
}
ul li a{
margin: 0 auto;
display: block;
60px;
height: 60px;
line-height: 50px;
box-sizing: border-box;
border-radius: 10px;
box-shadow: white;
text-align: center;
text-decoration: none;
color: white;
background: black;
}
ul li a:hover{
cursor: pointer;
color: saddlebrown;
}
#formula{
margin-left: -400px;
box-sizing: border-box;
border: 0;
margin-top: -60px;
position: absolute;
400px;
height: 20px;
}
</style>
</head>
<body>
<div id="calc">
<p>简易计算器</p>
<input class="f-text" type="text" readonly="readonly" maxlength="9" value="0" />
<ul>
<li class="btn-1"><a href="javascript:void(0)">c</a></li>
<li class="btn-1"><a href="javascript:void(0)">%</a></li>
<li class="btn-1"><a href="javascript:void(0)">/</a></li>
<li class="btn-1"><a href="javascript:void(0)">x</a></li>
<li><a href="javascript:void(0)">7</a></li>
<li><a href="javascript:void(0)">8</a></li>
<li><a href="javascript:void(0)">9</a></li>
<li class="btn-1"><a href="javascript:void(0)">-</a></li>
<li><a href="javascript:void(0)">4</a></li>
<li><a href="javascript:void(0)">5</a></li>
<li><a href="javascript:void(0)">6</a></li>
<li class="btn-1"><a href="javascript:void(0)">+</a></li>
<li><a href="javascript:void(0)">1</a></li>
<li><a href="javascript:void(0)">2</a></li>
<li><a href="javascript:void(0)">3</a></li>
<li class="btn-2"><a href="javascript:void(0)">=</a></li>
<li class="btn-3"><a href="javascript:void(0)">0</a></li>
<li><a href="javascript:void(0)">.</a></li>
<li><a href="javascript:void(0)">(</a></li>
<li><a href="javascript:void(0)">)</a></li>
</ul>
<input id="formula" type="text" readonly="readonly" value=""/>
</div>
</body>
</html>
<script>
var calc=document.getElementById("calc");
var a=calc.getElementsByTagName("a");
var input=calc.getElementsByTagName("input")[0];
var formula=document.getElementById("formula");
var s=false;
var i;
for(i=0;i<a.length;i++){
a[i].onfocus=function(){
this.blur()
};
a[i].onclick=function(){
switch(this.innerHTML){
case "c":
input.value=0;
formula.value="";
break;
case "%":
count("%")
break;
case "x":
count("*")
break;
case "-":
count("-")
break;
case "+":
count("+")
break;
case "(":
count("(")
break;
case ")":
count(")")
break;
case "=":
s || (formula.value+=input.value);
input.value=eval(formula.value.replace(/\%/*-+/,''));//输入的值进行运算后得到的值
input.value=input.value.substr(0,10).replace("NaN",0);//计算输入变量和输出结果最多前10位，如果不是数字返回0
s=true;
break;
case ".":
if(input.value.search(/[.\%/*-+]/)!=-1)//输入的值为非运算符时
break;
default:
s && (input.value=0,formula.value="",s=false);
input.value.length<10 &&(input.value=(input.value+this.innerHTML).replace(/^[0\%/*-+](d)/,"$1"));
}
}
}
function count(d){
var reg = /[\%/*-+]$/;
if(s)
{ //错误处理
formula.value=input.value + d;
input.value=d;
s=false;
}
else
{ //正确处理
reg.test(input.value) || (formula.value+=input.value);
console.log('3',/[\%/*-+]$/.test(input.value));
input.value=d;
console.log("n",input.value);
reg.test(formula.value) || (formula.value+=input.value);
formula.value=formula.value.slice(-1)!=d ? formula.value.replace(/.$/,d):formula.value
}
}
</script>