原生JavaScript结合Cookie实现购物车功能详解

<ul>
  <li><span>a0001</span><span>shdfi</span><span>￥98.00</span>
<input type="button" value="加入购物车"></li>
  <li><span>a0002</span><span>fbvfgdb</span><span>￥698.00</span>
<input type="button" value="加入购物车"></li>
  <li><span>a0003</span><span>dfdfi</span><span>￥988.00</span>
<input type="button" value="加入购物车"></li>
  <li><span>a0004</span><span>sssi</span><span>￥998.00</span>
<input type="button" value="加入购物车"></li>
  <li><span>a0005</span><span>yyu</span><span>￥98.00</span>
<input type="button" value="加入购物车"></li>
  <li><span>a0006</span><span>sheri</span><span>￥598.00</span>
<input type="button" value="加入购物车"></li>
  <li><span>a0007</span><span>dsfcdhdfi</span><span>￥498.00</span>
<input type="button" value="加入购物车"></li>
  <li><span>sbnm,</span><span>￥698.00</span><input type="button" value="加
入购物车"></li>
</ul>
<a href="购物车查看页面.html" rel="external nofollow" >查看购物车</a>

<script>
    //JSON.parse
    //JSON.stringify
    onload = function () {
      var input = document.getElementsByTagName("input");
      //判断是否存在cookie，或是第一次添加
      var arr = cookieUtil.getCookie("car") ? 
JSON.parse(cookieUtil.getCookie("car")) : [];
      //遍历给每个input元素添加点击事件
      for (var j = 0; j < input.length; j++) {
        input[j].onclick = function () {
          var g_id = this.parentNode.children[0].innerHTML;
          var g_name = this.parentNode.children[1].innerHTML;
          var g_price = this.parentNode.children[2].innerHTML;
          //遍历cookie，判断是否已经存在该商品
          for (var i = 0; i < arr.length; i++) {
            if (arr[i].g_id == g_id) {
              //已经存在该商品，商品数量+1
              arr[i].num++;
              break;//立即结束遍历
            }
          }
          //如果i的值与arr长度相同，则证明遍历结束也没有进入过if条件语句，
          //cookie中不存在该商品,新建一个商品对象，并添加到数组中
          if (i == arr.length) {
            var goods = {
              "g_id" : g_id,
              "g_name" : g_name,
              "g_price" : g_price,
              num : 1
            }
            arr.push(goods);
          }
          //把更新后的数组序列化为JSON字符串，保存到cookie中
          var date = new Date();
          date.setDate(date.getDate() + 10); //保存十天
  //保存cookie
  cookieUtil.setCookie("car", JSON.stringify(arr), date); 
        }
      }
    }
</script>

//cookie Util
var cookieUtil = {
  //添加cookie
  setCookie: function (name, value, expires) {
    var cookieText = encodeURIComponent(name) + "=" + 
encodeURIComponent(value);
    if (expires && expires instanceof Date) {
      cookieText += "; expires=" + expires;
    }
    // if (domain) {
    //   cookieText += "; domain=" + domain;
    // }
    document.cookie = cookieText;
  },
  //获取cookie
  getCookie: function (name) {
    var cookieText = decodeURIComponent(document.cookie);
    var cookieArr = cookieText.split("; ");
    for (var i = 0; i < cookieArr.length; i++) {
      var arr = cookieArr[i].split("=");
      if (arr[0] == name) {
        return arr[1];
      }
    }
    return null;
  },
  //删除cookie
  unsetCookie: function (name) {
    document.cookie = encodeURIComponent(name) + "=; expires=" + 
new Date(0);
  }
};

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>查看购物车页面</title>
  <script src="../Utils.js"></script>
  <script>
    onload = function () {
      var ul = document.getElementsByTagName("ul")[0];
      var arr = cookieUtil.getCookie("car");
      if (arr) {
        arr = JSON.parse(arr);
        //存在cookie则取出来显示到页面上
        for (var i = 0; i < arr.length; i++) {
          //每个数组元素对应的是一个商品对象
          var goods = arr[i];
          var li = document.createElement("li");
          li.innerHTML = "商品名称：" + goods.g_name + "，商品数
量" + goods.num + "，商品单价：" + goods.g_price;
          ul.appendChild(li);
        }
      } else {
        alert("购物车中还不存在商品！");
      }
    }
  </script>
</head>
<body>
<ul></ul>
</body>
</html>