CRUD operations & models integration

Now we’re tying together CRUD operations with models, which is the backbone of most Node.js backend apps, whether you use MongoDB/Mongoose or PostgreSQL/Sequelize. I’ll break it down step by step with a generic pattern you can adapt to either SQL or NoSQL.

---

1️⃣ Folder Structure Recap

src/
├── routes/
│   └── userRoutes.js
├── controllers/
│   └── userController.js
├── models/
│   └── User.js
├── app.js
└── server.js

• models/ → define your data structure

• controllers/ → implement CRUD logic

• routes/ → expose endpoints

---

2️⃣ CRUD Operations

Create (POST)

• Purpose: Add a new record to the database

// Controller: createUser
const createUser = async (req, res) => {
  try {
    const user = await User.create(req.body); // MongoDB/Mongoose
    // const user = await User.create(req.body); // Sequelize
    res.status(201).json(user);
  } catch (err) {
    res.status(400).json({ error: err.message });
  }
};

---

Read (GET)

• Purpose: Fetch data from the database

// Controller: getUsers
const getUsers = async (req, res) => {
  try {
    const users = await User.find(); // Mongoose
    // const users = await User.findAll(); // Sequelize
    res.json(users);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
};
 
// Controller: getUserById
const getUserById = async (req, res) => {
  try {
    const { id } = req.params;
    const user = await User.findById(id); // Mongoose
    // const user = await User.findByPk(id); // Sequelize
    if (!user) return res.status(404).json({ error: "User not found" });
    res.json(user);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
};

---

Update (PUT/PATCH)

• Purpose: Modify an existing record

const updateUser = async (req, res) => {
  try {
    const { id } = req.params;
    const user = await User.findByIdAndUpdate(id, req.body, { new: true }); // Mongoose
    // const user = await User.update(req.body, { where: { id }, returning: true }); // Sequelize
    if (!user) return res.status(404).json({ error: "User not found" });
    res.json(user);
  } catch (err) {
    res.status(400).json({ error: err.message });
  }
};

---

Delete (DELETE)

• Purpose: Remove a record

const deleteUser = async (req, res) => {
  try {
    const { id } = req.params;
    const user = await User.findByIdAndDelete(id); // Mongoose
    // const deleted = await User.destroy({ where: { id } }); // Sequelize
    if (!user) return res.status(404).json({ error: "User not found" });
    res.status(204).send(); // 204 = no content
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
};

---

3️⃣ Routes Integration

const express = require("express");
const router = express.Router();
const userController = require("../controllers/userController");
 
router.get("/", userController.getUsers);
router.get("/:id", userController.getUserById);
router.post("/", userController.createUser);
router.put("/:id", userController.updateUser);
router.delete("/:id", userController.deleteUser);
 
module.exports = router;

---

4️⃣ Model Integration Example

Mongoose Model (User.js)

const mongoose = require("mongoose");
 
const userSchema = new mongoose.Schema({
  name: { type: String, required: true },
  email: { type: String, required: true, unique: true },
  age: Number
});
 
module.exports = mongoose.model("User", userSchema);

Sequelize Model (User.js)

const { DataTypes } = require("sequelize");
const sequelize = require("../config/db");
 
const User = sequelize.define("User", {
  name: { type: DataTypes.STRING, allowNull: false },
  email: { type: DataTypes.STRING, allowNull: false, unique: true },
  age: DataTypes.INTEGER
});
 
module.exports = User;

---

5️⃣ Error Handling & Response Patterns

• Use try/catch for async errors

• Return consistent JSON format:

{
  "success": true,
  "data": {...},
  "error": null
}

• For errors:

{
  "success": false,
  "data": null,
  "error": "User not found"
}

---

✅ Summary

• CRUD = Create, Read, Update, Delete

• Controllers = implement CRUD logic using models

• Routes = expose endpoints for clients

• Models = define structure & validation of data (Mongoose or Sequelize)

• Error handling = try/catch + consistent JSON response

---