原生js实现淘宝购物车功能

js淘宝购物车功能描述：

1、点击“+”，单个商品数量加1，总数量加1；单个商品价格添加，总价也添加。
 2.点击“-”，单个商品数量减1，总数量减1；单个商品价格减少，总价也减少。
 当该商品数量为0时，点击依然为0；
 3.显示出总价，总数量和其中最贵的那个商品的价格。

瞄一眼效果图：

废话不多说，LU代码

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style>
*{padding:0;margin:0;}
#list,p{list-style:none;width:600px;margin:0 auto;}
#list li {width:600px;height:50px;line-height:50px;margin-top:20px;font-size:20px;}
#list li input{width:60px;height:40px;line-height:40px;}
.highlight{color:red;font-size:30px;font-weight:bold;}
</style>
<script>
window.onload = function () {

 var oUl = $('list');
 var totalNumber = $('totalNum');
 var totalPrice = $('totalPrice');
 var mostExpensive = $('mostExpensive');
 var aLi = oUl.getElementsByTagName('li');
 var maxPrice = [0];

 for ( var i = 0; i < aLi.length; i++ ) {
  price(aLi[i]);
 }

 function price(oLi) {

  var aBtn = oLi.getElementsByTagName('input');
  var oStrong = oLi.getElementsByTagName('strong')[0];
  var oEm = oLi.getElementsByTagName('em')[0];
  var oSpan = oLi.getElementsByTagName('span')[0];

  aBtn[0].onclick = function () {
   var num = Number(oStrong.innerHTML);
   var price = parseFloat(oEm.innerHTML);
   var numbers = Number(totalNumber.innerHTML);
   var prices = parseFloat(totalPrice.innerHTML);
   num--;
   if (num === 0) {
    // 如果该商品数量为0，,那么就得把它的价格从价格表中清除
    var index = maxPrice.indexOf(price);
    if (index > -1) maxPrice.splice(index, 1);
   } else if (num < 0) {
    num = 0;
    return;
   }
   numbers--;
   oStrong.innerHTML = num;
   oSpan.innerHTML = num * price + '元';
   totalNumber.innerHTML = numbers;
   totalPrice.innerHTML = prices - (num + 1) * price;
   mostExpensive.innerHTML = maxPrice[0];

  }
  aBtn[1].onclick = function () {

   var num = Number(oStrong.innerHTML);
   var price = parseFloat(oEm.innerHTML);
   var numbers = Number(totalNumber.innerHTML);
   var prices = parseFloat(totalPrice.innerHTML);

   num++;
   numbers++;
   if (maxPrice.indexOf(price) < 0) {
    maxPrice.push(price)
    maxPrice.sort(function (a,b) {return b - a});
   }
   oStrong.innerHTML = num;
   oSpan.innerHTML = num * price + '元';
   totalNumber.innerHTML = numbers;
   totalPrice.innerHTML = prices + num * price;
   mostExpensive.innerHTML = maxPrice[0];
  }
 }
 function $(id) {return document.getElementById(id);}
}
</script>
</head>

<body>
<ul id="list">
 <li>
  <input type="button" value="-" />
  <strong>0</strong>
  <input type="button" value="+" />
  单价：<em>12.5元</em>
  小计：<span class="highlight">0元</span>
 </li>
 <li>
  <input type="button" value="-" />
  <strong>0</strong>
  <input type="button" value="+" />
  单价：<em>10.5元</em>
  小计：<span class="highlight">0元</span>
 </li>
 <li>
  <input type="button" value="-" />
  <strong>0</strong>
  <input type="button" value="+" />
  单价：<em>8.5元</em>
  小计：<span class="highlight">0元</span>
 </li>
 <li>
  <input type="button" value="-" />
  <strong>0</strong>
  <input type="button" value="+" />
  单价：<em>8元</em>
  小计：<span class="highlight">0元</span>
 </li>
 <li>
  <input type="button" value="-" />
  <strong>0</strong>
  <input type="button" value="+" />
  单价：<em>14.5元</em>
  小计：<span class="highlight">0元</span>
 </li>
</ul>

<p>
商品合计共：<span class="highlight" id="totalNum">0</span>件，
共花费了：<span class="highlight" id="totalPrice">0</span>元<br />
其中最贵的商品单是：<span class="highlight" id="mostExpensive">0</span>元
</p>
</body>
</html>

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