问题：
1.页面第一次打开的，由于没有本地存储，不会调取数据，商品加1，不会加入购物车，但再加1 购物车一下 加2件，后面课正常加减
2.每一样商品添加第一件的时候 不会进入购物车 第2件的时候就加入了。

展示效果：https://ityanxi.github.io/seg...
代码地址：https://github.com/ityanxi/se...

js代码：

//获取元素
function $(id){
    return document.getElementById(id);
}
var table =$('cartTable'); // 购物车表格
var tr = table.children[1].rows; //行
var priceTotal = $('priceTotal'); //总计
var selectedTotal =$('selectedTotal'); //已选商品数目容器
var selectedViewList =  $('selectedViewList'); //浮层已选商品列表容器
var foot =  $('foot');
    
     
    
utils = {
    setParam : function (name,value){  //存储数据
        localStorage.setItem(name,value)  
    },  
    getParam : function(name){  //获取数据
        return localStorage.getItem(name)  
    }  
}  

product={  
    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");  //获取数据
            
        if (ShoppingCart == null || ShoppingCart == "") {  
            //第一次加入商品  
            var jsonstr = { "productlist": [{ 
                                            "name": product.name, //商品名称
                                            "num": product.num, //商品数量
                                            "price": product.price}], //商品单价
                            "totalNumber": product.num, //单一商品总数
                            "totalAmount": (product.price * product.num) //商品总价
            };
            
            
            //JSON.stringify(jsonstr)   //将json对象转换成字符串.
            utils.setParam("ShoppingCart", "'" + JSON.stringify(jsonstr));  //存储数据
           
             
        } else {  
            //JSON.parse(ShoppingCart.substr(1, ShoppingCart.length))//对json数据的解释    将字符串变成json对象
            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].name == product.name) {  
                    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({"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));  
           
            //保存购物车  
            utils.setParam("ShoppingCart", "'" + JSON.stringify(jsonstr));  
          
        }  
       
       
       
    },  
    //修改给买商品数量  
    updateproductnum: function (name, num) {  
        console.log(name,'+++：',num);
        var ShoppingCart = utils.getParam("ShoppingCart");  
        var jsonstr = JSON.parse(ShoppingCart.substr(1, ShoppingCart.length));  
        console.log(jsonstr);
        var productlist = jsonstr.productlist;  
  
        for (var i in productlist) {  
            if (productlist[i].name == name) {  
                jsonstr.totalNumber = parseInt(jsonstr.totalNumber) + (parseInt(num) - parseInt(productlist[i].num));  
                console.log(parseInt(jsonstr.totalNumber),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;  
                
                selectedTotal.innerHTML= orderdetail.totalNumber;
                priceTotal.innerHTML=(orderdetail.totalAmount).toFixed(2);//保留两位小数
                
                utils.setParam("ShoppingCart", "'" + JSON.stringify(jsonstr)); 
                
                console.log("'"+ 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 (name) {  
        var result = false;  
        var ShoppingCart = utils.getParam("ShoppingCart");  
        if (ShoppingCart != null) {  
            var jsonstr = JSON.parse(ShoppingCart.substr(1, ShoppingCart.length));  
            var productlist = jsonstr.productlist;  
            for (var i in productlist) {  
                if (productlist[i].name == name) {  
                    result = true;  
                }  
            }  
        }  
        return result;  
    },  
    //删除购物车中商品  
    deleteproduct: function (name) {  
        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].name == name) {  
                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));  
    }  
};  
    loadData()
    //加载数据
    function loadData(){
        if(localStorage.length>0){//如果有存储数据 则获取并渲染
            var productlist=cart.getproductlist();//取出购物车商品  
            var countInput = table.getElementsByClassName('count-input'); //数目input
            var goods=table.getElementsByClassName('goods');
            var names=[];
            for(var i=0;i<goods.length;i++){
                //console.log(goods[i].children[1].innerHTML);
                names.push(goods[i].children[1].innerHTML);
            }
            
            //var names=goods.children[1];
               //console.log(productlist);
             //console.log(names);
            
            for(var i=0;i<names.length;i++){
                for(var j=0;j<productlist.length;j++){
                    if(names[i]==productlist[j].name){
                        //console.log(i)
                        countInput[i].value=productlist[j].num
                    }
                    
                }
            }
            
               for(var i=0;i<productlist.length;i++){
                   console.log(productlist[i]);
                   
                   var str='    名称：'+productlist[i].name+'        数量：'+productlist[i].num+'        小计：'+(parseInt(product.num) * parseFloat(product.price))
                   console.log(str);
               }
            
            selectedTotal.innerHTML= orderdetail.totalNumber;
             priceTotal.innerHTML=(orderdetail.totalAmount).toFixed(2);//保留两位小数
        }else{
            return
        }
    }
    
  
    
    //为每行元素添加事件
    for (var i = 0; i < tr.length; i++) {
        //将点击事件绑定到tr元素
        tr[i].onclick = function (e) {
            var e = e || window.event;
            var el = e.target || e.srcElement; //通过事件对象的target属性获取触发元素
            var cls = el.className; //触发元素的class
            var countInout = this.getElementsByTagName('input')[0]; // 数目input
            var value = parseInt(countInout.value); //数目
            var goods=this.getElementsByClassName('goods')[0];
            var name=goods.children[1].innerHTML;
           
           
            var price=this.getElementsByClassName('price')[0].innerHTML;
            //通过判断触发元素的class确定用户点击了哪个元素
            switch (cls) {
                case 'add': //点击了加号
                    countInout.value = value + 1;
                    break;
                case 'reduce': //点击了减号
                    if (value > 0) {
                       countInout.value = value - 1;
                    }
                    break;
            }
            
           
            var product =  
                {  
                         //属性名用引号括起来，属性间由逗号隔开  
                    'name': name,  
                    'num':countInout.value,  
                    'price':price  
                };  
            console.log(product.num);
            
            if(cart.existproduct(product.name)){
                cart.updateproductnum(product.name,product.num);
            }else{
                
                cart.addproduct(product)
            }
            
           //loadData()
        }
    }
    
    


function remove1(){
        localStorage.removeItem("ShoppingCart")//删除变量名为key的存储变量 
    }