Role-based access control in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a middleware that checks if the user role is 'admin'.

Express

function checkAdmin(req, res, next) {
  if (req.user.role === '[1]') {
    next();
  } else {
    res.status(403).send('Access denied');
  }
}

Drag options to blanks, or click blank then click option'

Aadmin

Buser

Cguest

Dmoderator

Attempts:

3 left

💡 Hint

Common Mistakes

Using a role other than 'admin' will deny access incorrectly.

Forgetting to call next() when the role matches.

The middleware checks if req.user.role equals 'admin' to allow access.

2fill in blank

medium

Complete the code to apply the role check middleware to the '/dashboard' route.

Express

app.get('/dashboard', [1], (req, res) => {
  res.send('Welcome to dashboard');
});

Drag options to blanks, or click blank then click option'

AcheckUser

BroleCheck

CauthMiddleware

DcheckAdmin

Attempts:

3 left

💡 Hint

Common Mistakes

Using a middleware that does not check roles.

Forgetting to add middleware before the route handler.

The checkAdmin middleware is used to protect the dashboard route for admins only.

3fill in blank

hard

Fix the error in the middleware to correctly check if the user role is in allowed roles array.

Express

function authorize(allowedRoles) {
  return (req, res, next) => {
    if (allowedRoles.includes(req.user.[1])) {
      next();
    } else {
      res.status(403).send('Forbidden');
    }
  };
}

Drag options to blanks, or click blank then click option'

Arole

Broles

CuserRole

Dpermission

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong property name like 'roles' or 'permission'.

Not checking inclusion properly.

The user role is stored in req.user.role, so we check if it is included in allowedRoles.

4fill in blank

hard

Fill both blanks to create a middleware that authorizes roles 'editor' and 'admin'.

Express

const authorize = (roles) => {
  return (req, res, next) => {
    if (roles.[1](req.user.role)) {
      next();
    } else {
      res.status(403).send('[2]');
    }
  };
};

Drag options to blanks, or click blank then click option'

Aincludes

BForbidden

Cfind

Dfilter

Attempts:

3 left

💡 Hint

Common Mistakes

Using array methods that return arrays instead of booleans.

Sending wrong or unclear denial messages.

The includes method checks if the role is allowed. The message 'Forbidden' is sent on denial.

5fill in blank

hard

Fill all three blanks to create a route that uses the authorize middleware for 'admin' and 'editor' roles.

Express

app.post('/edit', [1](['[2]', '[3]']), (req, res) => {
  res.send('Edit page');
});

Drag options to blanks, or click blank then click option'

Aauthorize

Badmin

Ceditor

DcheckAdmin

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong middleware function name.

Passing roles as separate arguments instead of an array.

The authorize middleware is called with roles 'admin' and 'editor' to protect the '/edit' route.

Practice

1. What is the main purpose of role-based access control (RBAC) in an Express app?

easy

A. To speed up the server response time

B. To limit user actions based on their assigned roles

C. To store user passwords securely

D. To log all user activities automatically

Solution

1. Step 1: Understand RBAC concept

   RBAC means controlling what users can do depending on their role, like admin or guest.

2. Step 2: Identify main purpose in Express

   In Express, RBAC limits access to routes or actions based on user roles to keep the app safe.

3. Final Answer:

   To limit user actions based on their assigned roles -> Option B

4. Quick Check:

   RBAC controls user permissions = A [OK]

Hint: RBAC controls what users can do by role [OK]

Common Mistakes:

• Confusing RBAC with performance optimization
• Thinking RBAC stores passwords
• Assuming RBAC logs activities automatically

2. Which of the following is the correct way to define a middleware function in Express to check if a user has the role 'admin'?

easy

A. function checkAdmin(req, res, next) { if(req.user.role === 'admin') next(); else res.status(403).send('Forbidden'); }

B. function checkAdmin(req, res) { if(req.user.role == 'admin') next(); else res.send('Forbidden'); }

C. function checkAdmin(req, res, next) { if(req.user.role = 'admin') next(); else res.status(403).send('Forbidden'); }

D. function checkAdmin(req, res, next) { if(req.user.role !== 'admin') next(); else res.status(403).send('Forbidden'); }

Solution

1. Step 1: Check middleware signature

   Middleware must have three parameters: req, res, next.

2. Step 2: Verify role check and response

   function checkAdmin(req, res, next) { if(req.user.role === 'admin') next(); else res.status(403).send('Forbidden'); } correctly compares role with 'admin' using === and calls next() if true; else sends 403 status.

3. Final Answer:

   function checkAdmin(req, res, next) { if(req.user.role === 'admin') next(); else res.status(403).send('Forbidden'); } -> Option A

4. Quick Check:

   Middleware with correct params and strict role check = D [OK]

Hint: Middleware needs (req, res, next) and strict role check [OK]

Common Mistakes:

• Using assignment (=) instead of comparison (===)
• Missing next() parameter or call
• Wrong logic reversing role check

3. Given this Express route with role check middleware, what will be the response if a user with role 'user' tries to access it?

app.get('/admin', checkAdmin, (req, res) => { res.send('Welcome Admin'); });
function checkAdmin(req, res, next) {
  if(req.user.role === 'admin') next();
  else res.status(403).send('Forbidden');
}

medium

A. 403 Forbidden status with 'Forbidden' message

B. 'Welcome Admin'

C. 500 Internal Server Error

D. 404 Not Found

Solution

1. Step 1: Analyze middleware behavior for role 'user'

   The middleware checks if role is 'admin'. Since role is 'user', condition fails.

2. Step 2: Determine response when role check fails

   Middleware sends 403 status with 'Forbidden' message and does not call next(), so route handler is skipped.

3. Final Answer:

   403 Forbidden status with 'Forbidden' message -> Option A

4. Quick Check:

   Non-admin blocked with 403 Forbidden = B [OK]

Hint: Middleware blocks non-admin with 403, no next() call [OK]

Common Mistakes:

• Assuming route handler runs for non-admin
• Confusing 403 with 404 or 500 errors
• Ignoring middleware role check logic

4. Identify the error in this Express middleware for role-based access control:

function checkRole(req, res, next) {
  if(req.user.role = 'admin') {
    next();
  } else {
    res.status(403).send('Access denied');
  }
}

medium

A. Middleware missing req and res parameters

B. Missing next() call inside the else block

C. Incorrect status code for access denial

D. Using assignment (=) instead of comparison (===) in the if condition

Solution

1. Step 1: Check the if condition syntax

   The condition uses single = which assigns 'admin' to req.user.role instead of comparing it.

2. Step 2: Understand impact of assignment in condition

   Assignment always returns truthy, so else block never runs, causing wrong behavior.

3. Final Answer:

   Using assignment (=) instead of comparison (===) in the if condition -> Option D

4. Quick Check:

   Use === for comparison, not = [OK]

Hint: Use === for comparison, not = assignment [OK]

Common Mistakes:

• Confusing assignment and comparison operators
• Forgetting to call next() in middleware
• Using wrong HTTP status codes

5. You want to protect multiple routes so only users with roles 'admin' or 'manager' can access them. Which middleware implementation correctly allows this in Express?

hard

A. function checkRoles(req, res, next) { if(req.user.role === 'admin' && req.user.role === 'manager') next(); else res.status(403).send('Forbidden'); }

B. function checkRoles(req, res, next) { if(req.user.role === 'admin' || 'manager') next(); else res.status(403).send('Forbidden'); }

C. function checkRoles(req, res, next) { if(['admin', 'manager'].includes(req.user.role)) next(); else res.status(403).send('Forbidden'); }

D. function checkRoles(req, res, next) { if(req.user.role == 'admin' || req.user.role == 'manager') next(); else res.status(404).send('Forbidden'); }

Solution

1. Step 1: Check role inclusion logic

   function checkRoles(req, res, next) { if(['admin', 'manager'].includes(req.user.role)) next(); else res.status(403).send('Forbidden'); } uses array includes() to check if role is 'admin' or 'manager', which is correct and clean.

2. Step 2: Verify status code and logic correctness

   Using && requires role to be both 'admin' and 'manager' simultaneously (impossible); condition like if(role === 'admin' || 'manager') has wrong syntax and always passes since 'manager' is truthy; using 404 instead of 403 for forbidden access is incorrect.

3. Final Answer:

   function checkRoles(req, res, next) { if(['admin', 'manager'].includes(req.user.role)) next(); else res.status(403).send('Forbidden'); } -> Option C

4. Quick Check:

   Use includes() for multiple roles and 403 status = C [OK]

Hint: Use array includes() to check multiple roles cleanly [OK]

Common Mistakes:

• Using incorrect logical operators or syntax
• Checking role equality incorrectly
• Sending wrong HTTP status code for forbidden