로그인 기능 구현 app.js const express = require("express"); const mongoose = require("mongoose"); mongoose.set('strictQuery', true); const jwt = require('jsonwebtoken'); mongoose.connect("mongodb://127.0.0.1:27017/shopping-demo", { useNewUrlParser: true, useUnifiedTopology: true, }); const db = mongoose.connection; db.on("error", console.error.bind(console, "connection error:")); const app = express();..