# Node.js Express & PostgreSQL: CRUD Rest APIs example with Sequelize

### Node.js Rest CRUD API overview

We will build Rest Apis that can create, retrieve, update, delete and find Tutorials by title.

First, we start with an Express web server. Next, we add configuration for PostgreSQL database, create `Tutorial` model with Sequelize, write the controller. Then we define routes for handling all CRUD operations (including custom finder).

The following table shows overview of the Rest APIs that will be exported:

| Methods | Urls                      | Actions                                        |
| ------- | ------------------------- | ---------------------------------------------- |
| GET     | api/tutorials             | get all Tutorials                              |
| GET     | api/tutorials/:id         | get Tutorial by `id`                           |
| POST    | api/tutorials             | add new Tutorial                               |
| PUT     | api/tutorials/:id         | update Tutorial by `id`                        |
| DELETE  | api/tutorials/:id         | remove Tutorial by `id`                        |
| DELETE  | api/tutorials             | remove all Tutorials                           |
| GET     | api/tutorials/published   | find all published Tutorials                   |
| GET     | api/tutorials?title=\[kw] | find all Tutorials which title contains `'kw'` |

Finally, we’re gonna test the Rest Apis using Postman.

This is our project structure:

![node-js-express-sequelize-postgresql-project-structure](https://bezkoder.com/wp-content/uploads/2020/01/node-js-express-sequelize-postgresql-project-structure.png)

### Create Node.js App

First, we create a folder:

```
$ mkdir nodejs-express-sequelize-postgresql
$ cd nodejs-express-sequelize-postgresql
```

Next, we initialize the Node.js App with a *package.json* file:

```
npm init

name: (nodejs-express-sequelize-postgresql) 
version: (1.0.0) 
description: Node.js Rest Apis with Express, Sequelize & PostgreSQL.
entry point: (index.js) server.js
test command: 
git repository: 
keywords: nodejs, express, sequelize, postgresql, rest, api
author: bezkoder
license: (ISC)

Is this ok? (yes) yes
```

We need to install necessary modules: `express`, `sequelize`, `pg`, `pg-hstore` and `body-parser`.\
Run the command:

```
npm install express sequelize pg pg-hstore body-parser cors --save
```

\*`pg` for PostgreSQL and `pg-hstore` for converting data into the PostgreSQL hstore format.

The *package.json* file should look like this:

```
{
  "name": "nodejs-express-sequelize-postgresql",
  "version": "1.0.0",
  "description": "Node.js Rest Apis with Express, Sequelize & M",
  "main": "server.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [
    "nodejs",
    "express",
    "sequelize",
    "rest",
    "api",
    "postgresql"
  ],
  "author": "bezkoder",
  "license": "ISC",
  "dependencies": {
    "body-parser": "^1.19.0",
    "cors": "^2.8.5",
    "express": "^4.17.1",
    "pg": "^7.17.1",
    "pg-hstore": "^2.3.3",
    "sequelize": "^5.21.3"
  }
}
```

### Setup Express web server

In the root folder, let’s create a new *server.js* file:

```
const express = require("express");
const bodyParser = require("body-parser");
const cors = require("cors");

const app = express();

var corsOptions = {
  origin: "http://localhost:8081"
};

app.use(cors(corsOptions));

// parse requests of content-type - application/json
app.use(bodyParser.json());

// parse requests of content-type - application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({ extended: true }));

// simple route
app.get("/", (req, res) => {
  res.json({ message: "Welcome to bezkoder application." });
});

// set port, listen for requests
const PORT = process.env.PORT || 8080;
app.listen(PORT, () => {
  console.log(`Server is running on port ${PORT}.`);
});
```

What we do are:\
– import `express`, `body-parser` and `cors` modules:

* Express is for building the Rest apis
* [body-parser](https://www.npmjs.com/package/body-parser) helps to parse the request and create the `req.body` object
* [cors](https://www.npmjs.com/package/cors) provides Express middleware to enable CORS with various options.

– create an Express app, then add `body-parser` and `cors` middlewares using `app.use()` method. Notice that we set origin: `http://localhost:8081`.\
– define a GET route which is simple for test.\
– listen on port 8080 for incoming requests.

Now let’s run the app with command: `node server.js`.\
Open your browser with url <http://localhost:8080/>, you will see:

![node-js-express-sequelize-postgresql-example-setup-server](https://bezkoder.com/wp-content/uploads/2020/01/node-js-express-sequelize-postgresql-example-setup-server.png)

Yeah, the first step is done. We’re gonna work with Sequelize in the next section.

### Configure PostgreSQL database & Sequelize

In the *app* folder, we create a separate *config* folder for configuration with *db.config.js* file like this:

```
module.exports = {
  HOST: "localhost",
  USER: "postgres",
  PASSWORD: "123",
  DB: "testdb",
  dialect: "postgres",
  pool: {
    max: 5,
    min: 0,
    acquire: 30000,
    idle: 10000
  }
};
```

First five parameters are for PostgreSQL connection.\
`pool` is optional, it will be used for Sequelize connection pool configuration:

* `max`: maximum number of connection in pool
* `min`: minimum number of connection in pool
* `idle`: maximum time, in milliseconds, that a connection can be idle before being released
* `acquire`: maximum time, in milliseconds, that pool will try to get connection before throwing error

For more details, please visit [API Reference for the Sequelize constructor](https://sequelize.org/master/class/lib/sequelize.js~Sequelize.html#instance-constructor-constructor).

### Initialize Sequelize

We’re gonna initialize Sequelize in **app**/**models** folder that will contain model in the next step.

Now create **app**/**models**/*index.js* with the following code:

```
const dbConfig = require("../config/db.config.js");

const Sequelize = require("sequelize");
const sequelize = new Sequelize(dbConfig.DB, dbConfig.USER, dbConfig.PASSWORD, {
  host: dbConfig.HOST,
  dialect: dbConfig.dialect,
  operatorsAliases: false,

  pool: {
    max: dbConfig.pool.max,
    min: dbConfig.pool.min,
    acquire: dbConfig.pool.acquire,
    idle: dbConfig.pool.idle
  }
});

const db = {};

db.Sequelize = Sequelize;
db.sequelize = sequelize;

db.tutorials = require("./tutorial.model.js")(sequelize, Sequelize);

module.exports = db;
```

Don’t forget to call `sync()` method in *server.js*:

```
...
const app = express();
app.use(...);

const db = require("./app/models");
db.sequelize.sync();

...
```

In development, you may need to drop existing tables and re-sync database. Just use `force: true` as following code:

```

db.sequelize.sync({ force: true }).then(() => {
  console.log("Drop and re-sync db.");
});
```

### Define the Sequelize Model

In *models* folder, create *tutorial.model.js* file like this:

```
module.exports = (sequelize, Sequelize) => {
  const Tutorial = sequelize.define("tutorial", {
    title: {
      type: Sequelize.STRING
    },
    description: {
      type: Sequelize.STRING
    },
    published: {
      type: Sequelize.BOOLEAN
    }
  });

  return Tutorial;
};
```

This Sequelize Model represents **tutorials** table in PostgreSQL database. These columns will be generated automatically: *id*, *title*, *description*, *published*, *createdAt*, *updatedAt*.

After initializing Sequelize, we don’t need to write CRUD functions, Sequelize supports all of them:

* create a new Tutorial: [`create`](https://sequelize.org/master/class/lib/model.js~Model.html#static-method-create)`(object)`
* find a Tutorial by id: [`findByPk`](https://sequelize.org/master/class/lib/model.js~Model.html#static-method-findByPk)`(id)`
* get all Tutorials: [`findAll`](https://sequelize.org/master/class/lib/model.js~Model.html#static-method-findAll)`()`
* update a Tutorial by id: [`update`](https://sequelize.org/master/class/lib/model.js~Model.html#static-method-update)`(data, where: { id: id })`
* remove a Tutorial: [`destroy`](https://sequelize.org/master/class/lib/model.js~Model.html#static-method-destroy)`(where: { id: id })`
* remove all Tutorials: `destroy(where: {})`
* find all Tutorials by title: `findAll({ where: { title: ... } })`

These functions will be used in our Controller.

We can improve the example by adding Comments for each Tutorial. It is the One-to-Many Relationship and I write a tutorial for this at:\
[Node.js Sequelize Associations: One-to-Many example](https://bezkoder.com/sequelize-associate-one-to-many/)

Or you can add Tags for each Tutorial and add Tutorials to Tag (Many-to-Many Relationship):\
[Node.js Sequelize Associations: Many-to-Many example](https://bezkoder.com/sequelize-associate-many-to-many/)

### Create the Controller

Inside **app**/**controllers** folder, let’s create *tutorial.controller.js* with these CRUD functions:

* create
* findAll
* findOne
* update
* delete
* deleteAll
* findAllPublished

```
const db = require("../models");
const Tutorial = db.tutorials;
const Op = db.Sequelize.Op;

// Create and Save a new Tutorial
exports.create = (req, res) => {
  
};

// Retrieve all Tutorials from the database.
exports.findAll = (req, res) => {
  
};

// Find a single Tutorial with an id
exports.findOne = (req, res) => {
  
};

// Update a Tutorial by the id in the request
exports.update = (req, res) => {
  
};

// Delete a Tutorial with the specified id in the request
exports.delete = (req, res) => {
  
};

// Delete all Tutorials from the database.
exports.deleteAll = (req, res) => {
  
};

// Find all published Tutorials
exports.findAllPublished = (req, res) => {
  
};
```

Let’s implement these functions.

#### Create a new object

Create and Save a new Tutorial:

```
exports.create = (req, res) => {
  // Validate request
  if (!req.body.title) {
    res.status(400).send({
      message: "Content can not be empty!"
    });
    return;
  }

  // Create a Tutorial
  const tutorial = {
    title: req.body.title,
    description: req.body.description,
    published: req.body.published ? req.body.published : false
  };

  // Save Tutorial in the database
  Tutorial.create(tutorial)
    .then(data => {
      res.send(data);
    })
    .catch(err => {
      res.status(500).send({
        message:
          err.message || "Some error occurred while creating the Tutorial."
      });
    });
};
```

#### Retrieve objects (with condition)

Retrieve all Tutorials/ find by title from the database:

```
exports.findAll = (req, res) => {
  const title = req.query.title;
  var condition = title ? { title: { [Op.iLike]: `%${title}%` } } : null;

  Tutorial.findAll({ where: condition })
    .then(data => {
      res.send(data);
    })
    .catch(err => {
      res.status(500).send({
        message:
          err.message || "Some error occurred while retrieving tutorials."
      });
    });
};
```

We use `req.query.title` to get query string from the Request and consider it as condition for `findAll()` method.

#### Retrieve a single object

Find a single Tutorial with an `id`:

```
exports.findOne = (req, res) => {
  const id = req.params.id;

  Tutorial.findByPk(id)
    .then(data => {
      res.send(data);
    })
    .catch(err => {
      res.status(500).send({
        message: "Error retrieving Tutorial with id=" + id
      });
    });
};
```

#### Update an object

Update a Tutorial identified by the `id` in the request:

```
exports.update = (req, res) => {
  const id = req.params.id;

  Tutorial.update(req.body, {
    where: { id: id }
  })
    .then(num => {
      if (num == 1) {
        res.send({
          message: "Tutorial was updated successfully."
        });
      } else {
        res.send({
          message: `Cannot update Tutorial with id=${id}. Maybe Tutorial was not found or req.body is empty!`
        });
      }
    })
    .catch(err => {
      res.status(500).send({
        message: "Error updating Tutorial with id=" + id
      });
    });
};
```

#### Delete an object

Delete a Tutorial with the specified `id`:

```
exports.delete = (req, res) => {
  const id = req.params.id;

  Tutorial.destroy({
    where: { id: id }
  })
    .then(num => {
      if (num == 1) {
        res.send({
          message: "Tutorial was deleted successfully!"
        });
      } else {
        res.send({
          message: `Cannot delete Tutorial with id=${id}. Maybe Tutorial was not found!`
        });
      }
    })
    .catch(err => {
      res.status(500).send({
        message: "Could not delete Tutorial with id=" + id
      });
    });
};
```

#### Delete all objects

Delete all Tutorials from the database:

```
exports.deleteAll = (req, res) => {
  Tutorial.destroy({
    where: {},
    truncate: false
  })
    .then(nums => {
      res.send({ message: `${nums} Tutorials were deleted successfully!` });
    })
    .catch(err => {
      res.status(500).send({
        message:
          err.message || "Some error occurred while removing all tutorials."
      });
    });
};
```

#### Find all objects by condition

Find all Tutorials with `published = true`:

```
exports.findAllPublished = (req, res) => {
  Tutorial.findAll({ where: { published: true } })
    .then(data => {
      res.send(data);
    })
    .catch(err => {
      res.status(500).send({
        message:
          err.message || "Some error occurred while retrieving tutorials."
      });
    });
};
```

### Define Routes

When a client sends request for an endpoint using HTTP request (GET, POST, PUT, DELETE), we need to determine how the server will reponse by setting up the routes.

These are our routes:

* `/api/tutorials`: GET, POST, DELETE
* `/api/tutorials/:id`: GET, PUT, DELETE
* `/api/tutorials/published`: GET

Create a *turorial.routes.js* inside *app/routes* folder with content like this:

```
module.exports = app => {
  const tutorials = require("../controllers/tutorial.controller.js");

  var router = require("express").Router();

  // Create a new Tutorial
  router.post("/", tutorials.create);

  // Retrieve all Tutorials
  router.get("/", tutorials.findAll);

  // Retrieve all published Tutorials
  router.get("/published", tutorials.findAllPublished);

  // Retrieve a single Tutorial with id
  router.get("/:id", tutorials.findOne);

  // Update a Tutorial with id
  router.put("/:id", tutorials.update);

  // Delete a Tutorial with id
  router.delete("/:id", tutorials.delete);

  // Create a new Tutorial
  router.delete("/", tutorials.deleteAll);

  app.use('/api/tutorials', router);
};
```

You can see that we use a controller from `/controllers/tutorial.controller.js`.

We also need to include routes in *server.js* (right before `app.listen()`):

```
...

require("./app/routes/turorial.routes")(app);

// set port, listen for requests
const PORT = ...;
app.listen(...);
```

### Test the APIs

Run our Node.js application with command: `node server.js`.

Using Postman, we’re gonna test all the Apis above.

1.
2. **Create a new Tutorial using `POST /tutorials` Api**

   ![node-js-express-sequelize-postgresql-crud-create](https://bezkoder.com/wp-content/uploads/2020/01/node-js-express-sequelize-postgresql-crud-create.png)

   After creating some new Tutorials, you can check PostgreSQL table:

   ```
   testdb=# select * from tutorials;
    id |    title    |    description    | published |         createdAt          |         updatedAt
   ----+-------------+-------------------+-----------+----------------------------+----------------------------
     1 | Node Tut #1 | Tut#1 Description | f         | 2020-01-29 10:42:57.121+07 | 2020-01-29 10:42:57.121+07
     2 | Node Tut #2 | Tut#2 Description | f         | 2020-01-29 10:43:05.131+07 | 2020-01-29 10:43:05.131+07
     3 | Node Tut #3 | Tut#3 Description | f         | 2020-01-29 10:43:48.028+07 | 2020-01-29 10:43:48.028+07
     4 | Js Tut #4   | Tut#4 Desc        | f         | 2020-01-29 10:45:40.016+07 | 2020-01-29 10:45:40.016+07
     5 | Js Tut #5   | Tut#5 Desc        | f         | 2020-01-29 10:45:44.289+07 | 2020-01-29 10:45:44.289+07
   ```
3. **Retrieve all Tutorials using `GET /tutorials` Api**

   ![node-js-express-sequelize-postgresql-crud-retrieve](https://bezkoder.com/wp-content/uploads/2020/01/node-js-express-sequelize-postgresql-crud-retrieve.png)
4. **Retrieve a single Tutorial by id using `GET /tutorials/:id` Api**

   ![node-js-express-sequelize-postgresql-crud-get-by-id](https://bezkoder.com/wp-content/uploads/2020/01/node-js-express-sequelize-postgresql-crud-get-by-id.png)
5. **Update a Tutorial using `PUT /tutorials/:id` Api**

   ![node-js-express-sequelize-postgresql-crud-update](https://bezkoder.com/wp-content/uploads/2020/01/node-js-express-sequelize-postgresql-crud-update.png)

   Check `tutorials` table after some rows were updated:

   ```
   testdb=# select * from tutorials;
    id |     title      |    description    | published |         createdAt          |         updatedAt
   ----+----------------+-------------------+-----------+----------------------------+----------------------------
     1 | Node Tut #1    | Tut#1 Description | f         | 2020-01-29 10:42:57.121+07 | 2020-01-29 10:42:57.121+07
     3 | Node Tut #3    | Tut#3 Description | f         | 2020-01-29 10:43:48.028+07 | 2020-01-29 10:43:48.028+07
     2 | Node Js Tut #2 | Tut#2 Description | t         | 2020-01-29 10:43:05.131+07 | 2020-01-29 10:51:55.235+07
     4 | Js Tut #4      | Tut#4 Desc        | t         | 2020-01-29 10:45:40.016+07 | 2020-01-29 10:54:17.468+07
     5 | Js Tut #5      | Tut#5 Desc        | t         | 2020-01-29 10:45:44.289+07 | 2020-01-29 10:54:20.544+07
   ```
6. **Find all Tutorials which title contains ‘js’: `GET /tutorials?title=js`**

   ![node-js-express-sequelize-postgresql-crud-find-by-field](https://bezkoder.com/wp-content/uploads/2020/01/node-js-express-sequelize-postgresql-crud-find-by-field.png)
7. **Find all published Tutorials using `GET /tutorials/published` Api**

   ![node-js-express-sequelize-postgresql-crud-find-published](https://bezkoder.com/wp-content/uploads/2020/01/node-js-express-sequelize-postgresql-crud-find-published.png)
8. **Delete a Tutorial using `DELETE /tutorials/:id` Api**

   ![node-js-express-sequelize-postgresql-crud-delete](https://bezkoder.com/wp-content/uploads/2020/01/node-js-express-sequelize-postgresql-crud-delete.png)

   Tutorial with id=4 was removed from `tutorials` table:

   ```
   testdb=# select * from tutorials;
    id |     title      |    description    | published |         createdAt          |         updatedAt
   ----+----------------+-------------------+-----------+----------------------------+----------------------------
     1 | Node Tut #1    | Tut#1 Description | f         | 2020-01-29 10:42:57.121+07 | 2020-01-29 10:42:57.121+07
     3 | Node Tut #3    | Tut#3 Description | f         | 2020-01-29 10:43:48.028+07 | 2020-01-29 10:43:48.028+07
     2 | Node Js Tut #2 | Tut#2 Description | t         | 2020-01-29 10:43:05.131+07 | 2020-01-29 10:51:55.235+07
     5 | Js Tut #5      | Tut#5 Desc        | t         | 2020-01-29 10:45:44.289+07 | 2020-01-29 10:54:20.544+07
   ```
9. **Delete all Tutorials using `DELETE /tutorials` Api**

   ![node-js-express-sequelize-postgresql-crud-delete-all](https://bezkoder.com/wp-content/uploads/2020/01/node-js-express-sequelize-postgresql-crud-delete-all.png)

   Now there are no rows in `tutorials` table:

   ```
   testdb=# select * from tutorials;
    id | title | description | published | createdAt | updatedAt
   ----+-------+-------------+-----------+-----------+-----------
   ```
