基于html5 localStorage的购物车JS脚本

最近在做html5这一块，参考网上的代码写了一个购物车JS脚本，很简单，直接上代码，shoppingCart.js：

    utils = {            setParam : function (name,value){                localStorage.setItem(name,value)            },            getParam : function(name){                return localStorage.getItem(name)            }        }                product={            id:0,            name:"",            num:0,            price:0.00,        };        orderdetail={            username:"",            phone:"",            address:"",            zipcode:"",            totalNumber:0,            totalAmount:0.00            }        cart = {            //向购物车中添加商品            addproduct:function(product){                var ShoppingCart = utils.getParam("ShoppingCart");                if(ShoppingCart==null||ShoppingCart==""){                    //第一次加入商品                    var jsonstr = {"productlist":[{"id":product.id,"name":product.name,"num":product.num,"price":product.price}],"totalNumber":product.num,"totalAmount":(product.price*product.num)};                    utils.setParam("ShoppingCart","'"+JSON.stringify(jsonstr));                }else{                    var jsonstr = JSON.parse(ShoppingCart.substr(1,ShoppingCart.length));                    var productlist = jsonstr.productlist;                    var result=false;                    //查找购物车中是否有该商品                    for(var i in productlist){                        if(productlist[i].id==product.id){                            productlist[i].num=parseInt(productlist[i].num)+parseInt(product.num);                            result = true;                        }                    }                    if(!result){                        //没有该商品就直接加进去                        productlist.push({"id":product.id,"name":product.name,"num":product.num,"price":product.price});                    }                    //重新计算总价                    jsonstr.totalNumber=parseInt(jsonstr.totalNumber)+parseInt(product.num);                    jsonstr.totalAmount=parseFloat(jsonstr.totalAmount)+(parseInt(product.num)*parseFloat(product.price));                    orderdetail.totalNumber = jsonstr.totalNumber;                    orderdetail.totalAmount = jsonstr.totalAmount;                    //保存购物车                    utils.setParam("ShoppingCart","'"+JSON.stringify(jsonstr));                }            },            //修改给买商品数量            updateproductnum:function(id,num){                var ShoppingCart = utils.getParam("ShoppingCart");                var jsonstr = JSON.parse(ShoppingCart.substr(1,ShoppingCart.length));                var productlist = jsonstr.productlist;                                for(var i in productlist){                    if(productlist[i].id==id){                        jsonstr.totalNumber=parseInt(jsonstr.totalNumber)+(parseInt(num)-parseInt(productlist[i].num));                        jsonstr.totalAmount=parseFloat(jsonstr.totalAmount)+((parseInt(num)*parseFloat(productlist[i].price))-parseInt(productlist[i].num)*parseFloat(productlist[i].price));                        productlist[i].num=parseInt(num);                                                orderdetail.totalNumber = jsonstr.totalNumber;                        orderdetail.totalAmount = jsonstr.totalAmount;                        utils.setParam("ShoppingCart","'"+JSON.stringify(jsonstr));                        return;                    }                }            },            //获取购物车中的所有商品            getproductlist:function(){                var ShoppingCart = utils.getParam("ShoppingCart");                var jsonstr = JSON.parse(ShoppingCart.substr(1,ShoppingCart.length));                var productlist = jsonstr.productlist;                orderdetail.totalNumber = jsonstr.totalNumber;                orderdetail.totalAmount = jsonstr.totalAmount;                return productlist;            },            //判断购物车中是否存在商品            existproduct:function(id){                var ShoppingCart = utils.getParam("ShoppingCart");                var jsonstr = JSON.parse(ShoppingCart.substr(1,ShoppingCart.length));                var productlist = jsonstr.productlist;                var result=false;                for(var i in productlist){                    if(productlist[i].id==product.id){                        result = true;                    }                }                return result;            },            //删除购物车中商品            deleteproduct:function(id){                var ShoppingCart = utils.getParam("ShoppingCart");                var jsonstr = JSON.parse(ShoppingCart.substr(1,ShoppingCart.length));                var productlist = jsonstr.productlist;                var list=[];                for(var i in productlist){                    if(productlist[i].id==id){                        jsonstr.totalNumber=parseInt(jsonstr.totalNumber)-parseInt(productlist[i].num);                        jsonstr.totalAmount=parseFloat(jsonstr.totalAmount)-parseInt(productlist[i].num)*parseFloat(productlist[i].price);                    }else{                        list.push(productlist[i]);                    }                }                jsonstr.productlist = list;                orderdetail.totalNumber = jsonstr.totalNumber;                orderdetail.totalAmount = jsonstr.totalAmount;                utils.setParam("ShoppingCart","'"+JSON.stringify(jsonstr));            }        };  

var product =    {        'id': id,        //属性名用引号括起来，属性间由逗号隔开        'name': 'hhh',        'num':jq('#text-4').val(),        'price':199.9    };    //商品加入到购物车    cart.addproduct(product);    var productlist=cart.getproductlist();//取出购物车商品    alert('', '商品:'+productlist[0].id+' '+productlist[0].name+' '+productlist[0].num+' '+productlist[0].price, '确定');