resolving the issue

.gitignore

@@ -0,0 +1,23 @@
+# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+
+# dependencies
+/node_modules
+/.pnp
+.pnp.js
+
+# testing
+/coverage
+
+# production
+/build
+
+# misc
+.DS_Store
+.env.local
+.env.development.local
+.env.test.local
+.env.production.local
+
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*

backend/config.js

@@ -0,0 +1,3 @@
+module.exports = {
+  JWT_SECRET: "secret",
+};

backend/db.js

@@ -0,0 +1,50 @@
+const mongoose = require("mongoose");
+
+mongoose.connect(
+  "mongodb+srv://tanishsingla51:9313111030Aa%[email protected]/paytm"
+);
+
+const userSchema = new mongoose.Schema({
+  username: {
+    type: String,
+    required: true,
+    lowercase: true,
+    unique: true,
+    minLength: 3,
+    maxLength: 20,
+  },
+  password: {
+    type: String,
+    required: true,
+    minLength: 6,
+  },
+  firstName: {
+    type: String,
+    required: true,
+    minLength: 3,
+    maxLength: 20,
+  },
+  lastName: {
+    type: String,
+    required: true,
+    minLength: 3,
+    maxLength: 20,
+  },
+});
+
+const accountSchema = new mongoose.Schema({
+  userId: {
+    type: mongoose.Schema.Types.ObjectId,
+    ref: "User",
+    required: true,
+  },
+  balance: {
+    type: Number,
+    required: true,
+  },
+});
+
+const User = mongoose.model("User", userSchema);
+const Account = mongoose.model("Account", accountSchema);
+
+module.exports = { User, Account };

backend/index.js

@@ -1,3 +1,14 @@
 const express = require("express");
+const mainRouter = require("./routes/index");
+const cors = require("cors");
 
+const app = express();
 
+app.use(cors());
+app.use(express.json());
+
+app.use("/api/v1", mainRouter);
+
+app.listen(3000, () => {
+  console.log("Server is running on port 3000");
+});

backend/middleware.js

@@ -0,0 +1,30 @@
+const { JWT_SECRET } = require("./config");
+const jwt = require("jsonwebtoken");
+
+const authMiddleware = (req, res, next) => {
+  const authHeader = req.headers.authorization;
+
+  if (!authHeader || !authHeader.startsWith("Bearer ")) {
+    return res.status(403).json({
+      msg: "Unauthorized",
+    });
+  }
+
+  const token = authHeader.split(" ")[1];
+
+  try {
+    const decoded = jwt.verify(token, JWT_SECRET);
+
+    req.userId = decoded.userId; //
+
+    next();
+  } catch (err) {
+    return res.status(403).json({
+      msg: err.message,
+    });
+  }
+};
+
+module.exports = {
+  authMiddleware,
+};