前言

相信大家都很熟悉商品购物车这一功能，每当我们在某宝某东上购买商品的时候，看中了哪件商品，就会加入购物车中，最后结算。购物车这一功能，方便消费者对商品进行管理，可以添加商品，删除商品，选中购物车中的某一项或几项商品，最后商品总价也会随着消费者的操作随着变化。本文介绍的是通过Javascript实现类似于淘宝的购物车效果，包括商品的单选、全选、删除、修改数量、价格计算、数目计算、预览等功能。

功能如下

1. 实现兼容低版本IE的getElementsByClassName()方法

2. JS表格操作

3. 通过parseInt() ，parseFloat()把字符串转换成数字

4. 通过toFixed()把数字格式化成指定位数的小数

5. 事件代理的运用

效果图：

border-collapse有两个值可以选择，分别是collapse和separate，就是合并边框和分离边框，分离边框之下又可以设置间距和边框样式

border-spacing:2em 4em;（设置右间距和下间距）

border-style:none solid dashed dotted;（分别设置上右下左的样式）

html结构：

<table id="cartTable">
 <thead>
 <tr>
 <th><label><input class="check-all check" type="checkbox"/> 全选</label></th>
 <th>商品</th>
 <th>单价</th>
 <th>数量</th>
 <th>小计</th>
 <th>操作</th>
 </tr>
 </thead>
 <tbody>
 <tr>
 <td class="checkbox"><input class="check-one check" type="checkbox" /></td>
 <td class="goods"><img src="images/1.jpg" alt="" /><span>Casio/卡西欧 EX-TR350</span></td>
 <td class="price">5999.88</td>
 <td class="count"><span class="reduce"></span><input class="count-input" type="text" value="1"/>
 <span class="add">+</span></td>
 <td class="subtotal">5999.88</td>
 <td class="operation"><span class="delete">删除</span></td>
 </tr>
 <tr>
 <td class="checkbox"><input class="check-one check" type="checkbox" /></td>
 <td class="goods"><img src="images/2.jpg" alt="" /><span>Canon/佳能 PowerShot SX50 HS</span></td>
 <td class="price">3888.50</td>
 <td class="count"><span class="reduce"></span><input class="count-input" type="text" value="1"/>
 <span class="add">+</span></td>
 <td class="subtotal">3888.50</td>
 <td class="operation"><span class="delete">删除</span></td>
 </tr>
 <tr>
 <td class="checkbox"><input class="check-one check" type="checkbox" /></td>
 <td class="goods"><img src="images/3.jpg" alt="" /><span>Sony/索尼 DSC-WX300</span></td>
 <td class="price">1428.50</td>
 <td class="count"><span class="reduce"></span><input class="count-input" type="text" value="1"/>
 <span class="add">+</span></td>
 <td class="subtotal">1428.50</td>
 <td class="operation"><span class="delete">删除</span></td>
 </tr>
 <tr>
 <td class="checkbox"><input class="check-one check" type="checkbox" /></td>
 <td class="goods"><img src="images/4.jpg" alt="" /><span>Fujifilm/富士 instax mini 25</span></td>
 <td class="price">0.60</td>
 <td class="count"><span class="reduce"></span><input class="count-input" type="text" value="1"/>
 <span class="add">+</span></td>
 <td class="subtotal">0.60</td>
 <td class="operation"><span class="delete">删除</span></td>
 </tr>
 </tbody>
</table>
<p class="foot" id="foot">
 <label class=" fl select-all"><input type="checkbox" class="check-all check" /> 全选</label>
 <a class="fl delete" id="deleteAll" href="javascript:;" rel="external nofollow" >删除</a>
 <p class="fr closing">结 算</p>
 <p class="fr total">合计：￥<span id="priceTotal">0.00</span></p>
 <p class="fr select" id="selected">已选商品<span id="selectedTotal">0</span>件<span class="arrow up">︽</span><span class="arrow down">︾</span></p>
 <p class="selected-view">
 <p id="selectedViewList" class="clearfix">
 <p><img src="images/1.jpg"><span>取消选择</span></p>
 </p>
 <span class="arrow">◆<span>◆</span></span>
 </p>
</p>

css代码：

*{
 margin: 0;
 padding: 0;
 }
 a{
 color: #666;
 text-decoration: none;
 }
 body{
 padding:20px;
 color: #666;
 }
 .fl{
 float: left;
 }
 .fr{
 float: right;
 }
 table{
 border-collapse: collapse;
 border-spacing: 0;
 border: 0;
 text-align: center;
 width: 937px;
 }
 th,td{
 border: 1px solid #cadeff;
 }
 th{
 background: #e2f2ff;
 border-top: 3px solid #a7cbff;
 height: 30px;
 }
 td{
 padding: 10px;
 color: #444;
 }
 tbody tr:hover{
 background: RGB(238,246,255);
 }
 .checkbox{width: 60px;}
 .goods{width: 300px;}
 .goods span{
 width: 180px;
 margin-top: 20px;
 text-align: left;
 float: left;
 }
 .price{width: 130px;}
 .count{width: 90px;}
 .count .add, .count input, .count .reduce{
 float: left;
 margin-left: -1px;
 position: relative;
 z-index: 0;
 }
 .count .add, .count .reduce{
 height: 23px;
 width: 17px;
 border: 1px solid #e5e5e5;
 background: #f0f0f0;
 text-align: center;
 line-height: 23px;
 color: #444;
 }
 .count .add:hover, .count .reduce:hover{
 color: #f50;
 z-index: 3;
 border-color: #f60;
 cursor: pointer;
 }
 .count input{
 width: 50px;
 height: 15px;
 line-height: 15px;
 border: 1px solid #aaa;
 color: #343434;
 text-align: center;
 padding: 4px 0;
 background-color: #fff;
 z-index: 2;
 }
 .subtotal{
 width: 150px;
 color: red;
 font-weight: bold;
 }
 .operation{width: 80px;}
 .operation span:hover, .a:hover{
 cursor: pointer;
 color: red;
 text-decoration: underline;
 }
 img{
 width: 100px;
 height: 80px;
 margin-right: 10px;
 float: left;
 }
 .foot{
 width: 935px;
 margin-top: 10px;
 color: #666;
 height: 48px;
 border: 1px solid #c8c8c8;
 background-image: linear-gradient(RGB(241,241,241),RGB(226,226,226));
 position: relative;
 z-index: 8;
 }
 .foot p, .foot a{
 line-height: 48px;
 height: 48px;
 }
 .foot .select-all{
 width: 100px;
 height: 48px;
 line-height: 48px;
 padding-left: 5px;
 color: #666;
 }
 .foot .closing{
 border-left: 1px solid #c8c8c8;
 width: 100px;
 text-align: center;
 color: #000;
 font-weight: bold;
 background: RGB(238,238,238);
 cursor: pointer;
 }
 .foot .total{
 margin: 0 20px;
 cursor: pointer;
 }
 .foot #priceTotal, .foot #selectedTotal{
 color: red;
 font-family: "微软雅黑";
 font-weight: bold;
 }
 .foot .select{
 cursor: pointer;
 }
 .foot .select .arrow{
 position: relative;
 top: -3px;
 margin-left: 3px;
 }
 .foot .select .down{
 position: relative;
 top: 3px;
 display: none;
 }
 .show .select .down{
 display: inline;
 }
 .show .select .up{
 display: none;
 }
 .foot .select:hover .arrow{
 color: red;
 }
 .foot .selected-view{
 width: 935px;
 border: 1px solid #c8c8c8;
 position: absolute;
 height: auto;
 background: #fff;
 z-index: 9;
 bottom: 48px;
 left: -1px;
 display: none;
 }
 .show .selected-view{display: block;}
 .foot .selected-view p{height: auto;}
 .foot .selected-view .arrow{
 font-size: 16px;
 line-height: 100%;
 color: #c8c8c8;
 position: absolute;
 right: 330px;
 bottom: -9px;
 }
 .foot .selected-view .arrow span{
 color: #fff;
 position: absolute;
 left: 0;
 bottom: 1px;
 }
 #selectedViewList{
 padding: 20px;
 margin-bottom: -20px;
 }
 #selectedViewList p{
 display: inline-block;
 position: relative;
 width: 100px;
 height: 80px;
 border: 1px solid #ccc;
 margin: 10px;
 }
 #selectedViewList p span{
 display: none;
 color: #fff;
 font-size: 12px;
 position: absolute;
 top: 0;
 right: 0;
 width: 60px;
 height: 18px;
 line-height: 18px;
 text-align: center;
 background: RGBA(0,0,0,.5);
 cursor: pointer;
 }
 #selectedViewList p:hover span{
 display: block;
 }

js部分：

1）实现商品的全选功能及数量和价格的计算

2)点击已选商品实现商品预览浮层的功能

点击已选商品时会显示出已选择商品的列表

同时在getTotal()函数中增加新创建的p

js代码：

3)商品列表中的取消选择与事件代理

已选商品列表中没有appendChild的时候p和span都不存在，所以要使用事件代理。

4）实现增减商品数量及小计价格的计算

5）实现删除商品功能

学会用for循环删除数组中的一些数据时要回置下标 i 。

总结