jQuery's method of implementing a shopping cart based on json and cookies_jquery

[{'ProductID':ABC','Num':'1'},{'ProductID':DEF,'Num':'2'}]

/*
添加商品及数量到购物车cookie中,返回当前商品在cookie中的总数
*/
function AddToShoppingCar(id, num) {
  var _num = 1;
  if (num != undefined)
    _num = num;
  var totalNum = _num; //总数默认为传入参数
  var cookieSet = { expires: 7, path: '/' }; //设置cookie路径的
//  $.cookie(cookieProductID, null, cookieSet);//清除Cookie
  var jsonStr = "[{'ProductID':'" + id + "','Num':'" + _num + "'}]"; //构造json字符串,id是商品id  num是这个商品的数量
  if ($.cookie(cookieProductID) == null) {
    $.cookie(cookieProductID, jsonStr, cookieSet); //如果没有这个cookie就设置他
  }
  else {
    var jsonObj = eval('(' + $.cookie(cookieProductID) + ')'); //如果有，把json字符串转换成对象
    var findProduct = false;//是否找到产品ID,找到则为TRUE,否则为FALSH
    for (var obj in jsonObj) {
      if (jsonObj[obj].ProductID == id) {
        jsonObj[obj].Num = Number(jsonObj[obj].Num) + _num;
        totalNum = jsonObj[obj].Num;
        findProduct = true;
        break;
      }
    }
    if (findProduct == false) { //没找到,则添加
      jsonObj[jsonObj.length] = new Object();
      jsonObj[jsonObj.length - 1].ProductID = id;
      jsonObj[jsonObj.length - 1].Num = num;
    }
    $.cookie(cookieProductID, JSON.stringify(jsonObj), cookieSet); //写入coockie  JSON需要json2.js支持
  }
  return totalNum;
  //  alert($.cookie(cookieProductID));
}

//以下为cookie插件代码
jQuery.cookie = function(name, value, options) {
  if (typeof value != 'undefined') { // name and value given, set cookie
    options = options || {};
    if (value === null) {
      value = '';
      options.expires = -1;
    }
    var expires = '';
    if (options.expires && (typeof options.expires == 'number' || options.expires.toUTCString)) {
      var date;
      if (typeof options.expires == 'number') {
        date = new Date();
        date.setTime(date.getTime() + (options.expires * 24 * 60 * 60 * 1000));
      } else {
        date = options.expires;
      }
      expires = '; expires=' + date.toUTCString(); // use expires attribute, max-age is not supported by IE
    }
    var path = options.path ? '; path=' + options.path : '';
    var domain = options.domain ? '; domain=' + options.domain : '';
    var secure = options.secure ? '; secure' : '';
    document.cookie = [name, '=', encodeURIComponent(value), expires, path, domain, secure].join('');
  } else { // only name given, get cookie
    var cookieValue = null;
    if (document.cookie && document.cookie != '') {
      var cookies = document.cookie.split(';');
      for (var i = 0; i < cookies.length; i++) {
        var cookie = jQuery.trim(cookies[i]);
        // Does this cookie string begin with the name we want&#63;
        if (cookie.substring(0, name.length + 1) == (name + '=')) {
          cookieValue = decodeURIComponent(cookie.substring(name.length + 1));
          break;
        }
      }
    }
    return cookieValue;
  }
};