Token generation and validation in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the JWT module in a NestJS service.

NestJS

import { [1] } from '@nestjs/jwt';

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AJwtStrategy

BJwtModule

CJwtGuard

DJwtService

Attempts:

3 left

💡 Hint

Common Mistakes

Importing JwtModule instead of JwtService

Using JwtGuard which is for authorization

Using JwtStrategy which is for passport strategies

The JwtService is imported from @nestjs/jwt to generate and validate tokens.

2fill in blank

medium

Complete the code to generate a JWT token with a payload.

NestJS

const token = this.jwtService.[1](payload);

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AsignAsync

Bsign

Cdecode

Dverify

Attempts:

3 left

💡 Hint

Common Mistakes

Using verify or decode instead of sign

Using signAsync when synchronous sign is intended

The sign method creates a JWT token synchronously from the payload.

3fill in blank

hard

Fix the error in the code to verify a JWT token.

NestJS

const payload = this.jwtService.[1](token);

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Adecode

Bsign

Cverify

DsignAsync

Attempts:

3 left

💡 Hint

Common Mistakes

Using decode which does not validate

Using sign which creates tokens

Using signAsync which is for signing

The verify method checks the token's validity and returns the decoded payload.

4fill in blank

hard

Fill both blanks to create a JWT token with expiration and secret options.

NestJS

const token = this.jwtService.sign(payload, { [1]: '1h', [2]: 'mySecretKey' });

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AexpiresIn

Bsecret

Calgorithm

Daudience

Attempts:

3 left

💡 Hint

Common Mistakes

Using algorithm or audience instead of expiresIn or secret

Mixing up option names

The expiresIn option sets token expiry time, and secret defines the signing key.

5fill in blank

hard

Fill all three blanks to decode a token safely with error handling.

NestJS

try {
  const payload = this.jwtService.[1](token, { [2]: 'mySecretKey' });
  return payload;
} catch (error) {
  throw new [3]('Invalid token');
}

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Averify

Bsecret

CUnauthorizedException

Ddecode

Attempts:

3 left

💡 Hint

Common Mistakes

Using decode which does not validate

Not providing the secret key

Throwing generic errors instead of UnauthorizedException

Use verify to check the token with the secret. If invalid, throw UnauthorizedException to signal access denial.