JWT token verification middleware in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the JWT library.

Express

const jwt = require('[1]');

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Acors

Bjsonwebtoken

Cexpress

Dbody-parser

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'express' instead of 'jsonwebtoken' for JWT handling.

Trying to import a package that is unrelated to JWT.

The jsonwebtoken package is used to work with JWT tokens in Express.

2fill in blank

medium

Complete the code to extract the token from the Authorization header.

Express

const token = req.headers.authorization && req.headers.authorization.split(' ')[[1]];

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A1

B0

C2

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Using index 0 which gives 'Bearer' instead of the token.

Using index 2 which is out of range.

The Authorization header usually has the format 'Bearer <token>'. Splitting by space, the token is at index 1.

3fill in blank

hard

Fix the error in the token verification call.

Express

jwt.verify(token, process.env.JWT_SECRET, ([1], decoded) => {
  if (error) {
    return res.status(401).json({ message: 'Unauthorized' });
  }
  req.user = decoded;
  next();
});

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Aerror

Be

Cerr

Dexception

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different parameter name than the one checked inside the callback.

Not matching the error parameter with the variable used in the if condition.

The callback function parameter for errors is commonly named error here to match the usage inside the function.

4fill in blank

hard

Fill both blanks to create the middleware function and export it.

Express

function [1](req, res, next) {
  // middleware code here
}

module.exports = [2];

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AverifyToken

BauthMiddleware

CverifyTokenMiddleware

DtokenVerifier

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the function and export.

Using generic names that don't describe the middleware purpose.

The function is named verifyToken and exported with the same name for clarity and usage.

5fill in blank

hard

Fill all three blanks to complete the middleware that verifies the JWT token and handles errors.

Express

function verifyToken(req, res, next) {
  const token = req.headers.authorization && req.headers.authorization.split(' ')[[1]];
  if (!token) {
    return res.status(401).json({ message: '[2]' });
  }
  jwt.verify(token, process.env.JWT_SECRET, (error, decoded) => {
    if (error) {
      return res.status(401).json({ message: '[3]' });
    }
    req.user = decoded;
    next();
  });
}

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A1

BNo token provided

CInvalid token

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong index for token extraction.

Using unclear or incorrect error messages.

The token is at index 1 after splitting the Authorization header. The error messages clearly indicate missing or invalid tokens.