js网页简易计算器
野路子新人学习过程中的产物，参照知乎上的一篇文章里的练习做的（第三课第七个），有不符合科班出身常识的地方请指正。
因为大幅改过布局，所以会有些比较奇怪的标签用法，见谅。
截图：
布局：
<body>
<div id="Cbody">
<p id="name">By-mirai2333p>
<div id="displayArea">0div>
<p id="num">p>
<div>
<ul>
<button class="clear">Cbutton>
<button class="symbols">%button>
<button class="symbols">/button>
<button class="symbols">*button>
<button class="numbers">7button>
<button class="numbers">8button>
<button class="numbers">9button>
<button class="symbols">-button>
<button class="numbers">4button>
<button class="numbers">5button>
<button class="numbers">6button>
<button class="symbols">+button>
<button class="numbers">1button>
<button class="numbers">2button>
<button class="numbers">3button>
<button class="equal">=button>
<button class="zero">0button>
<button class="numbers">.button>
ul>
div>
div>
body>样式：
<style type="text/css">
body{text-align: center;color: white;overflow: hidden;}
p{margin: 0px;height: 20px;}
ul{margin: 0px 0px 15px 12px;padding: 0px;position: relative;overflow: hidden;}
button{margin: 16px 12px 0px 0px;padding: 0px; float: left;width: 60px;height: 40px;font-size: 20px;}
#name{height: 20px;margin: 0px 3px 0px 3px;text-align: right;}
#Cbody{width: 300px;height: 400px;background: black;margin: auto;}
#displayArea{height: 84px;font:700 50px/100px Arial;background: #EEEEE0;color: black;text-align: right;}
#num{font: 100 15px/20px Arial;position: absolute;top: 28px;left: 618px;width: 300px;height: 20px;color: black;text-align: right;}
.zero{width: 132px;}
.equal{height: 96px;position: absolute;bottom: 0px;right: 0px;}
style>js的思路是这样的：所有的操作都是针对显示部分，显示部分分为当前显示和已经成型的表达式。（以下简称为“当前”和“已经”）
共有三个状态：
- 当前是数字，已经是符号或空（发生在键入符号后再键入数字，或初始状态）
- 当前和已经都是符号（发生在键入符号后）
- 当前和已经都是数字（发生在键入等号后）
三类按钮“数字”“符号”“等号”的onclick事件都是按照上述三个状态进行处理，“等号”把要计算的表达式整理放入已经，然后用eval()函数计算。
JavaScript：
<script type="text/javascript">
window.onload=function(){
var current = document.getElementById('displayArea');
var already = document.getElementById('num');
var buttons = document.getElementsByTagName('button');
for (var i = 0; i < buttons.length; i++) {
//数字键的单击事件
if (buttons[i].className=="numbers"||buttons[i].className=="zero") {
buttons[i].onclick=function(){
//外层循环是为了配合里面的替换，处理符号加点的情况
if (!(/[\%\/\*\-\+]$/.test(current.innerText)&&this.innerHTML==".")) {
if (current.innerText.length<10) {
current.innerText+=this.innerHTML;
var text = current.innerText.replace(/^[0\%\/\*\-\+](\d)/,"$1");
current.innerText=text;
}
}
}
//符号键的单击事件
}else if (buttons[i].className=="symbols") {
buttons[i].onclick=function(){
//对应状态二，此时要把旧符号换成新的，依旧是状态二
if (/[\%\/\*\-\+]$/.test(current.innerText)) {
var text = already.innerHTML.replace(/([\%\/\*\-\+])$/,this.innerHTML);
already.innerHTML=text;
current.innerText=this.innerHTML;
//对应状态一，此时把当前数字移入已经并添加符号，变成状态二
}else if (/[\%\/\*\-\+\=]$/.test(already.innerHTML)){
already.innerHTML+=current.innerText+this.innerHTML;
current.innerText=this.innerHTML;
//对应状态三，把结果移入已经并添加符号，变成状态二
}else{
already.innerHTML = current.innerText+this.innerHTML;
current.innerText = this.innerHTML
}
}
//清除
}else if(buttons[i].className=="clear"){
buttons[i].onclick=function(){
already.innerHTML="";
current.innerText="0";
}
//等号
}else{
buttons[i].onclick=function(){
//状态二，去除符号并计算显示
if (/[\%\/\*\-\+\=]$/.test(current.innerText)) {
var text = already.innerHTML.replace(/([\%\/\*\-\+])$/,"");
already.innerHTML=text;
var text = eval(already.innerHTML);
current.innerText=text.toString().substr(0,10);
//状态一，当前移入已经并计算显示
}else if (/[\%\/\*\-\+\=]$/.test(already.innerHTML)) {
already.innerHTML+=current.innerText;
current.innerText=this.innerHTML;
var text = eval(already.innerHTML);
current.innerText=text.toString().substr(0,10);
}
}
}
}
}
script>下面附上知乎大佬的代码作为参考：
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style>
body,div,p,ul,li,input{margin:0;padding:0;}
ul{list-style-type:none;}
a{color:#fff;outline:none;text-decoration:none;}
body{font:700 24px/1.5 Arial;}
#calc{position:relative;width:300px;background:#000;margin:10px auto;}
#calc p{color:#fff;text-align:right;font:12px/20px Arial;padding:0 5px;}
#calc .f-text{border:0;width:290px;height:84px;text-align:right;font:700 50px/84px Arial;background:url(img/inputBg.jpg) repeat-x;padding:0 5px;}
#calc ul{position:relative;overflow:hidden;zoom:1;background:url(img/bg.jpg);padding:0 0 17px 8px;}
#calc ul li{float:left;width:63px;height:41px;margin:17px 10px 0 0;}
#calc ul li a{display:block;width:63px;height:41px;line-height:41px;text-align:center;background:url(img/btn.png) no-repeat;}
#calc ul li a:hover{background-position:-63px 0;}
#calc ul li.btn-1 a{background-position:0 -41px;}
#calc ul li.btn-1 a:hover{background-position:-63px -41px;}
#calc ul li.btn-2{position:absolute;top:174px;right:0;height:99px;}
#calc ul li.btn-2 a{height:99px;line-height:99px;background-position:0 -164px;}
#calc ul li.btn-2 a:hover{background-position:-63px -164px;}
#calc ul li.btn-3{width:136px;}
#calc ul li.btn-3 a{width:136px;background-position:0 -82px;}
#calc ul li.btn-3 a:hover{background-position:0 -123px;}
#formula{position:absolute;top:20px;background:none;border:0;font:700 12px/1.5 Arial;width:280px;padding:3px 15px 0 5px;text-align:right;}
style>
<script>
window.onload = function ()
{
var oCalc = document.getElementById("calc");
var aA = oCalc.getElementsByTagName("a");
var aInput = oCalc.getElementsByTagName("input")[0];
var oFormula = document.getElementById("formula");
var s = false;
var i = 0;
for (i = 0; i < aA.length; i++){
aA[i].onfocus = function ()
{
this.blur()
};
aA[i].onclick = function ()
{
switch(this.innerHTML)
{
case "c":
aInput.value = 0;
oFormula.value = "";
break;
case "%":
count("%")
break;
case "÷":
count("/")
break;
case "×":
count("*")
break;
case "-":
count("-")
break;
case "+":
count("+")
break;
case "=":
s || (oFormula.value += aInput.value);
aInput.value = eval(oFormula.value.replace(/\%\/\*\-\+/,''));
aInput.value = aInput.value.substr(0,10).replace("NaN",0);
s = true;
break;
case ".":
if(aInput.value.search(/[\.\%\/\*\-\+]/) != -1)
break;
default:
s && (aInput.value = 0, oFormula.value = "", s = false);
aInput.value.length < 10 && (aInput.value = (aInput.value + this.innerHTML).replace(/^[0\%\/\*\-\+](\d)/,"$1"));
}
}
}
function count(a)
{
if(s)
{
oFormula.value = aInput.value + a;
aInput.value = a;
s = false;
}
else
{
/[\%\/\*\-\+]$/.test(aInput.value) || (oFormula.value += aInput.value);
aInput.value = a;
/[\%\/\*\-\+]$/.test(oFormula.value) || (oFormula.value += aInput.value);
oFormula.value = oFormula.value.slice(-1) != a ? oFormula.value.replace(/.$/,a) : oFormula.value
}
}
}
script>
<title>网页计算器title>
head>
<body>
<div id="calc">
<p>By - Ferris QQ:21314130p>
<input class="f-text" type="text" readonly="readonly" maxlength="9" value="0" />
<ul>
<li class="btn-1"><a href="javascript:void(0)">ca>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)">×a>li>
<li><a href="javascript:void(0)">7a>li>
<li><a href="javascript:void(0)">8a>li>
<li><a href="javascript:void(0)">9a>li>
<li class="btn-1"><a href="javascript:void(0)">-a>li>
<li><a href="javascript:void(0)">4a>li>
<li><a href="javascript:void(0)">5a>li>
<li><a href="javascript:void(0)">6a>li>
<li class="btn-1"><a href="javascript:void(0)">+a>li>
<li><a href="javascript:void(0)">1a>li>
<li><a href="javascript:void(0)">2a>li>
<li><a href="javascript:void(0)">3a>li>
<li class="btn-2"><a href="javascript:void(0)">=a>li>
<li class="btn-3"><a href="javascript:void(0)">0a>li>
<li><a href="javascript:void(0)">.a>li>
ul>
<input id="formula" type="text" readonly="readonly" value="" />
div>
body>
html>大佬的截图：
