How to implement floating shopping cart using js+cookies

// JavaScript Document
//计算单个小计
 function EveryCount()
 {
  var index=window.event.srcElement.parentElement.parentElement.rowIndex;
  var a=document.getElementById("test").rows(index).cells(1).innerText;
  var b=document.getElementById("Num"+index).value;
  var c=parseFloat(a)*parseFloat(b);
  document.getElementById("test").rows(index).cells(3).innerText=c;
  TotalCount();
  updateOrderCookie();//修改cookies中保存的数量
 }
//计算总计
function TotalCount()
{
  var rowscount=document.getElementById("test").rows.length;
  var sum=0;
  for(var i=1;i<=(parseInt(rowscount)-1);i++)
  {
    var littecount=document.getElementById("test").rows(i).cells(3).innerText;
    sum=parseFloat(sum)+parseFloat(littecount);
  }
  document.getElementById("total").innerText=sum;
}
//<--Start--将订单数据写入div
function WriteOrderInDiv()
{
 var gwc="<table id=&#39;test&#39; style=&#39;border:0px;&#39; ><tr><td width=&#39;40%&#39;>商品名称</td><td>单价(￥)</td><td>数量</td><td>小计</td></tr>";
 var OrderString=unescape(ReadOrderForm(&#39;24_OrderForm&#39;));//获取cookies中的购物车信息
 //document.write(OrderString);
 var strs= new Array(); //定义一个数组，用于存储购物车里的每一条信息
 var OneOrder="";
 //strs=OrderString.split("%7C");//用|分割出购物车中的每个产品
 strs=OrderString.split("|");//用|分割出购物车中的每个产品
 for (i=1;i<strs.length ;i++ )  
 {
 gwc+="<tr>";
 //OneOrder=strs[i].split("%26");
 OneOrder=strs[i].split("&");
 for (a=1;a<OneOrder.length ;a++ )  
 {
  if(a!=3)
  {
  gwc+="<td>";
  gwc+=OneOrder[a];
  gwc+="</td>";
  }
  else
  {
  gwc+="<td id=&#39;dd&#39;>";
  gwc+="<input title=&#39;填写想购买的数量,请使用合法数字字符&#39; style=&#39;width:10px;&#39; id=&#39;Num"+i+"&#39; type=&#39;text&#39; onkeyup=&#39;EveryCount();&#39;value=&#39;"+OneOrder[a]+"&#39;>";
  gwc+="</td>";
  }
  //document.getElementById("gwc").innerHTML+=OneOrder[a]+"<br/>";//每个产品的每个属性分割后字符输出
 }
 gwc+="<td>";
  gwc+=OneOrder[2]*OneOrder[3];
  gwc+="</td>";
  gwc+="</tr>";
    //document.getElementById("gwc").innerHTML+=strs[i]+"<br/>";  //每个产品分割后的字符输出
  }
 gwc+="</table>";
 document.getElementById("Cart").innerHTML=gwc;
 TotalCount();
}
//<--End--将订单数据写入div
//--Start--展开/收缩购物车
function show(id)
{
if (document.getElementById(id).style.display=="") 
{
document.getElementById(id).style.display=&#39;none&#39;;
}
else{document.getElementById(id).style.display=&#39;&#39;;
}
}
//<--End--展开/收缩购物车
//<--Start--从cookie中读出订单数据的函数
function ReadOrderForm(name)
{
  var cookieString=document.cookie;
  if (cookieString=="")
  {
    return false;
  }
  else
  {
    var firstChar,lastChar;
    firstChar=cookieString.indexOf(name);
    if(firstChar!=-1)
    {
      firstChar+=name.length+1;
      lastChar = cookieString.indexOf(&#39;;&#39;, firstChar);
      if(lastChar == -1) lastChar=cookieString.length;
      return cookieString.substring(firstChar,lastChar);
    }
    else
    {
      return false;
    }
  }  
}
//-->End
//<--Start--添加商品至购物车的函数,参数(商品编号,商品名称，商品数量，商品单价)
function SetOrderForm(item_no,item_name,item_amount,item_price)
{
  var cookieString=document.cookie;
  if (cookieString.length>=4000)
  {
    alert("您的订单已满\n请结束此次订单操作后添加新订单！");
  }
  else if(item_amount<1||item_amount.indexOf(&#39;.&#39;)!=-1)
  {
    alert("数量输入错误！");
  }
  else
  {
    var mer_list=ReadOrderForm(&#39;24_OrderForm&#39;);
    var Then = new Date();
    Then.setTime(Then.getTime()+30*60*1000);
    var item_detail="|"+item_no+"&"+item_name+"&"+item_price+"&"+item_amount;
    if(mer_list==false)
    {
      document.cookie="24_OrderForm="+escape(item_detail)+";expires=" + Then.toGMTString();
      alert("“"+item_name+"”\n"+"已经加入您的订单！");
    }
    else
    {
      if (mer_list.indexOf(escape(item_no))!=-1)
      {
        alert(&#39;此商品您已添加\n请进入订单修改数量！&#39;)
      }
      else
      {
        document.cookie="24_OrderForm="+mer_list+escape(item_detail)+";expires=" + Then.toGMTString();
        alert("“"+item_name+"”\n"+"已经加入您的订单！");
      }
    }
  }
}
//-->End
//<--Start--修改数量后，更新cookie的函数
function updateOrderCookie()
{
 var rowscount=document.getElementById("test").rows.length;
  var item_detail="";
  for(var i=1;i<=(parseInt(rowscount)-1);i++)
  {
    item_detail+="|"+document.getElementById("test").rows(i).cells(0).innerText+"&"+document.getElementById("test").rows(i).cells(0).innerText+"&"+document.getElementById("test").rows(i).cells(1).innerText+"&"+document.getElementById("Num"+i).value;
   // document.write(document.getElementById("test").rows(i).cells(1).innerText);
  }
 var Then = new Date();
 Then.setTime(Then.getTime()+30*60*1000);
 document.cookie="24_OrderForm="+escape(item_detail)+";expires=" + Then.toGMTString();
}
//<--End--订单更新
//<--清空购物车
function clearOrder() 
{
var Then = new Date();
document.cookie="24_OrderForm=&#39;&#39;;expires=" + Then.toGMTString();
}
//<--End

<script src="js/gwc.js" type="text/javascript"></script>
<div width="300px">
 <div id="Cart" style="line-height: 24px; font-size: 12px; background-color: #f0f0f0;
 border-top: 1px #ffffff solid；display:none; ">
 </div>
 <div id="Info">
      总计：<strong><span id="total" style="color: #FF0000; font-size: 36px">0</span></strong>元
  <input type="button" value="清空" onclick="clearOrder();WriteOrderInDiv();" />
  <input type="button" value="展开/收缩" onclick="show(&#39;Cart&#39;)" />
 </div>
 <input type="button" value="加入商品1" onclick="SetOrderForm(&#39;NO1&#39;,&#39;商品1&#39;,&#39;1&#39;,&#39;3.5&#39;);WriteOrderInDiv();" />
 <input type="button" value="加入商品2" onclick="SetOrderForm(&#39;NO2&#39;,&#39;商品2&#39;,&#39;1&#39;,&#39;5.5&#39;);WriteOrderInDiv();" />
 <input type="button" value="加入商品3" onclick="SetOrderForm(&#39;NO3&#39;,&#39;商品3&#39;,&#39;1&#39;,&#39;10.5&#39;);WriteOrderInDiv();" />
 </div>
  <script>
  window.WriteOrderInDiv();
  </script>