DTO pattern for data transfer in Express - Mini Project: Build & Apply

DTO Pattern for Data Transfer in Express

📖 Scenario: You are building a simple Express server that manages user data. To keep your code clean and safe, you want to use the DTO (Data Transfer Object) pattern. This means you will create a special object that only sends the needed user information to the client, hiding sensitive details like passwords.

🎯 Goal: Build an Express route that sends user data using a DTO object. The DTO will include only the user's id, name, and email, excluding the password.

📋 What You'll Learn

Create a user object with id, name, email, and password

Create a UserDTO class that takes a user object and stores only id, name, and email

Create an Express route /user that returns the UserDTO as JSON

Use the DTO pattern to send only safe user data to the client

💡 Why This Matters

🌍 Real World

Using DTOs helps protect sensitive data when sending information from a server to a client, which is important in real web applications to keep user data safe.

💼 Career

Understanding and implementing the DTO pattern is a common task for backend developers working with APIs, especially in Node.js and Express environments.

1

Create the user data object

Create a constant called user with these exact properties and values: id set to 1, name set to "Alice", email set to "[e-mail]", and password set to "secret123".

Express

# Your code here

Need a hint?

Use const user = { id: 1, name: "Alice", email: "[e-mail]", password: "secret123" }.

2

Create the UserDTO class

Create a class called UserDTO with a constructor that takes one parameter user. Inside the constructor, set this.id to user.id, this.name to user.name, and this.email to user.email. Do not include the password.

Express

const user = {
  id: 1,
  name: "Alice",
  email: "[e-mail]",
  password: "secret123"
};

// Your code here

Need a hint?

Define class UserDTO with a constructor that copies only id, name, and email from the user.

3

Set up Express and create the /user route

Import Express by writing import express from 'express'. Create an Express app by calling express() and store it in a constant called app. Then create a GET route at /user that sends a new UserDTO created from the user object as JSON.

Express

const user = {
  id: 1,
  name: "Alice",
  email: "[e-mail]",
  password: "secret123"
};

class UserDTO {
  constructor(user) {
    this.id = user.id;
    this.name = user.name;
    this.email = user.email;
  }
}

// Your code here

Need a hint?

Use import express from 'express', then const app = express(), and create a GET route with app.get('/user', (req, res) => { res.json(new UserDTO(user)) }).

4

Start the Express server

Add a line to start the Express server by calling app.listen on port 3000. Inside the listen callback, log the string "Server running on port 3000".

Express

import express from 'express';

const user = {
  id: 1,
  name: "Alice",
  email: "[e-mail]",
  password: "secret123"
};

class UserDTO {
  constructor(user) {
    this.id = user.id;
    this.name = user.name;
    this.email = user.email;
  }
}

const app = express();

app.get('/user', (req, res) => {
  res.json(new UserDTO(user));
});

// Your code here

Need a hint?

Use app.listen(3000, () => { console.log("Server running on port 3000") }) to start the server.