求解：vue2.0商城开发中后台添加成功，前端返回添加失败？

Question

前端代码： <li v-for="(itme,index) in GoodList"> <div class="pic"> <a href="#"><img v-lazy="'/static/'+itme.productImage" alt=""></a> </div> <div class="main"> <div class="name">{{itme.productName}}</div> <div class="price">{{itme.salePrice}}</div> <div class="btn-area"> <a href="javascript:;" class="btn btn--m" @click="addCart(itme.productId)">加入购物车</a> </div> </div> </li> addCart(productId){ axios.post('/goods/addCart',{productId:productId}).then((res)=>{ if(res.status==0){ alert("添加成功"); }else{ alert("msg:"+res.msg); } })后端代码：///加入购物车router.post("/addCart", function(req, res, next) { var userId = "100000077"; var productId = req.body.productId; var User = require('../models/user'); User.findOne({ userId: userId }, function(err, userDoc) { if(err) { res.json({ status: "1", msg: err.message }) } else { if(userDoc) { console.log("userDoc:" + userDoc); let goodsItem = ''; userDoc.cartList.forEach(function(item) { if(item.productId == productId) { goodsItem = item; item.productNum++; } }); if(goodsItem) { userDoc.save(function(err2, doc2) { if(err2) { res.json({ status: "1", msg: err2.message }); } else { res.json({ status: "0", msg: "", result: "suc" }); } }) } else { Goods.findOne({ productId: productId }, function(err1, doc) { if(err1) { res.json({ status: "1", msg: err1.message }); } else { if(doc) { newobj = { //新创建一个对象，实现转换mongoose不能直接增加属性的坑 productId: doc.productId, producName: doc.producName, salePrice: doc.salePrice, productName: doc.productName, productImage: doc.productImage, productNum: "1", checked: "1", } userDoc.cartList.push(newobj); userDoc.save(function(err2, doc2) { if(err2) { res.json({ status: "1", msg: err2.message }); } else { res.json({ status: "0", msg: "", result: "suc" }); } }) } } }); } } } });});