Local strategy (username/password) in NestJS - Mini Project: Build & Apply

Local Strategy (username/password) Authentication in NestJS

📖 Scenario: You are building a simple NestJS backend that allows users to log in using a username and password. This is a common way websites check who you are before letting you access private information.We will create a local authentication strategy that checks the username and password against a small list of users stored in the code.

🎯 Goal: Build a NestJS local strategy that verifies a username and password from a predefined list of users.When a user tries to log in, the system will check if the username and password match one of the users and allow access if correct.

📋 What You'll Learn

Create a list of users with usernames and passwords

Add a configuration variable for password minimum length

Implement the local strategy to validate username and password

Complete the strategy class with necessary decorators and methods

💡 Why This Matters

🌍 Real World

Local username/password authentication is a common way to secure web applications by verifying user identity before granting access.

💼 Career

Understanding how to implement authentication strategies in NestJS is essential for backend developers building secure APIs and services.

1

Create the users list

Create a constant array called users with these exact user objects: { username: 'john', password: 'changeme' } and { username: 'maria', password: 'guess' }.

NestJS

# Create the users array with two user objects
# Your code here

Need a hint?

Use const users = [ ... ] and include the exact user objects inside the array.

2

Add password minimum length config

Create a constant called MIN_PASSWORD_LENGTH and set it to 6.

NestJS

const users = [
  { username: 'john', password: 'changeme' },
  { username: 'maria', password: 'guess' }
];

# Define the minimum password length
# Your code here

Need a hint?

Use const MIN_PASSWORD_LENGTH = 6; to set the minimum password length.

3

Implement validate method in LocalStrategy

Create a class called LocalStrategy with a method validate(username: string, password: string) that returns the user object if the username and password match a user in users. Return null if no match is found or if the password length is less than MIN_PASSWORD_LENGTH.

NestJS

const users = [
  { username: 'john', password: 'changeme' },
  { username: 'maria', password: 'guess' }
];

const MIN_PASSWORD_LENGTH = 6;

# Create LocalStrategy class with validate method
# Your code here

Need a hint?

Use users.find to locate the user and check password length before returning.

4

Complete LocalStrategy with decorator and export

Add the @Injectable() decorator above the LocalStrategy class and export the class with export class LocalStrategy.

NestJS

const users = [
  { username: 'john', password: 'changeme' },
  { username: 'maria', password: 'guess' }
];

const MIN_PASSWORD_LENGTH = 6;

# Add @Injectable() decorator and export the LocalStrategy class
# Your code here

Need a hint?

Import Injectable from @nestjs/common and add @Injectable() above the class. Use export class LocalStrategy.