Navigation guards (beforeEach, beforeEnter) in Vue - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when a global beforeEach guard blocks navigation?

Consider a Vue Router setup with a beforeEach guard that checks if a user is authenticated. If not, it redirects to a login page.

What will be the rendered output if a user tries to visit a protected route without being authenticated?

Vue

router.beforeEach((to, from, next) => {
  if (!isAuthenticated() && to.name !== 'login') {
    next({ name: 'login' });
  } else {
    next();
  }
})

A The user is immediately redirected to the login page without seeing the protected page.

B The user sees the protected page content briefly, then is redirected to login.

C The navigation is blocked and the user stays on the current page with no change.

D The router throws an error because next() is called twice.

💡 Hint

Think about when next() is called with a redirect object.

The beforeEach guard intercepts navigation before the route changes. If the user is not authenticated, calling next({ name: 'login' }) immediately redirects to the login page without rendering the protected page.

❓ state_output

intermediate

What is the value of 'accessGranted' after beforeEnter guard runs?

Given a route with a beforeEnter guard that sets a variable accessGranted to true only if a query parameter token equals 'abc123'. What is the value of accessGranted after navigating to /dashboard?token=abc123?

Vue

let accessGranted = false;
const routes = [
  {
    path: '/dashboard',
    beforeEnter: (to, from, next) => {
      if (to.query.token === 'abc123') {
        accessGranted = true;
        next();
      } else {
        next(false);
      }
    }
  }
];

A false

B true

C null

D undefined

💡 Hint

Check the condition inside the beforeEnter guard and the query parameter value.

The beforeEnter guard sets accessGranted to true only if the query parameter token equals 'abc123'. Since the URL has ?token=abc123, the condition is true and accessGranted becomes true.

📝 Syntax

advanced

Which option causes a syntax error in a beforeEach guard?

Identify which beforeEach guard code snippet will cause a syntax error in Vue Router.

A router.beforeEach((to, from, next) => { if (to.meta.requiresAuth) { next(); } else { next(false); } })

B router.beforeEach((to, from, next) => { if (to.meta.requiresAuth) next(); else next(false); })

C router.beforeEach((to, from, next) => { if to.meta.requiresAuth { next(); } else { next(false); } })

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💡 Hint

Look carefully at the syntax of the if statement.

Option C is missing parentheses around the if condition, which is required in JavaScript syntax. This causes a syntax error.

🔧 Debug

advanced

Why does navigation get stuck when using next() incorrectly?

In a beforeEach guard, the code calls next() twice under certain conditions. What is the effect on navigation?

Vue

router.beforeEach((to, from, next) => {
  if (to.name === 'home') {
    next();
    next(false);
  } else {
    next();
  }
})

A Navigation proceeds normally to the 'home' route.

B Navigation is aborted and the user stays on the current page.

C Navigation proceeds but with a warning in the console.

D Navigation causes an error and the app crashes.

💡 Hint

Check what happens if next() is called more than once.

Calling next() multiple times in the same guard causes Vue Router to throw an error and can crash the app or break navigation.

🧠 Conceptual

expert

Which guard type runs first during navigation in Vue Router?

Vue Router supports multiple navigation guards: beforeEach, beforeEnter, and component guards like beforeRouteEnter. Which guard runs first when navigating to a new route?

A <code>beforeEach</code> global guard

B <code>beforeEnter</code> guard on the route

C Component's <code>beforeRouteEnter</code> guard

D After navigation is confirmed

💡 Hint

Think about the order of global vs route-specific guards.

The global beforeEach guard runs first before any route-specific beforeEnter or component guards. This allows global checks before entering any route.

Practice

1. What is the main purpose of Vue Router's beforeEach navigation guard?

easy

A. To run a function before every route change globally

B. To run a function only after a route has been entered

C. To modify the route's component before rendering

D. To delay the route change indefinitely

Solution

1. Step 1: Understand the role of beforeEach

   beforeEach is a global navigation guard that runs before every route change in the app.

2. Step 2: Compare options with the guard's behavior

   To run a function before every route change globally correctly states it runs before every route change globally. Other options describe incorrect or unrelated behaviors.

3. Final Answer:

   To run a function before every route change globally -> Option A

4. Quick Check:

   Global guard before route change = A [OK]

Hint: beforeEach runs before every route change globally [OK]

Common Mistakes:

• Confusing beforeEach with afterEach
• Thinking beforeEach runs only on specific routes
• Assuming beforeEach modifies components directly

2. Which of the following is the correct syntax to add a beforeEnter guard to a route in Vue Router?

easy

A. { path: '/home', component: Home, beforeEnter(to, from, next) { next() } }

B. { path: '/home', component: Home, beforeEnter: function(to, from, next) { next() } }

C. { path: '/home', component: Home, beforeEnter: (to, from, next) => { next() } }

D. router.beforeEnter('/home', (to, from, next) => next())

Solution

1. Step 1: Identify correct route object syntax

   Vue Router expects beforeEnter as a property with a function value inside the route object.

2. Step 2: Check each option's syntax

   { path: '/home', component: Home, beforeEnter: function(to, from, next) { next() } } uses beforeEnter: function(to, from, next) { next() } which is valid. { path: '/home', component: Home, beforeEnter(to, from, next) { next() } } misses the colon. { path: '/home', component: Home, beforeEnter: (to, from, next) => { next() } } uses arrow function which is valid but less common in examples. router.beforeEnter('/home', (to, from, next) => next()) is invalid syntax for route config.

3. Final Answer:

   { path: '/home', component: Home, beforeEnter: function(to, from, next) { next() } } -> Option B

4. Quick Check:

   Route guard syntax uses colon and function = C [OK]

Hint: Use colon and function for beforeEnter in route object [OK]

Common Mistakes:

• Omitting colon before beforeEnter
• Trying to call beforeEnter on router instance
• Using arrow function without colon

3. Given this Vue Router setup, what will happen when navigating to /dashboard?

const router = createRouter({
  history: createWebHistory(),
  routes: [
    { path: '/login', component: Login },
    { path: '/dashboard', component: Dashboard, beforeEnter(to, from, next) {
      if (!isLoggedIn()) next('/login')
      else next()
    } }
  ]
})

router.beforeEach((to, from, next) => {
  console.log('Global guard')
  next()
})

medium

A. Navigation blocked with no console output

B. Console logs 'Global guard' and navigates to /dashboard regardless

C. Console logs 'Global guard' and navigates to /login if not logged in

D. Syntax error due to missing next() call

Solution

1. Step 1: Analyze global beforeEach guard

   The global guard logs 'Global guard' and calls next(), so navigation proceeds.

2. Step 2: Analyze route-specific beforeEnter guard

   beforeEnter checks if user is logged in. If not, it redirects to '/login'. Otherwise, it allows navigation.

3. Final Answer:

   Console logs 'Global guard' and navigates to /login if not logged in -> Option C

4. Quick Check:

   Global guard logs + route guard redirects if not logged in = A [OK]

Hint: Global guard runs first, then route guard decides next step [OK]

Common Mistakes:

• Ignoring global guard console log
• Assuming navigation always succeeds
• Forgetting next() call in guards

4. Identify the error in this Vue Router navigation guard code:

router.beforeEach((to, from, next) => {
  if (to.meta.requiresAuth) {
    if (!userIsLoggedIn) {
      next('/login')
    }
  }
  next()
})

medium

A. Missing call to next() inside the if block causes navigation to continue twice

B. userIsLoggedIn should be a function call

C. to.meta.requiresAuth is not a valid property

D. next() is called twice, causing navigation to fail

Solution

1. Step 1: Trace next() calls in the guard

   If to.meta.requiresAuth is true and user is not logged in, next('/login') is called. Then outside the if block, next() is called again unconditionally.

2. Step 2: Understand consequences of calling next() twice

   Calling next() twice causes Vue Router to throw an error and navigation fails.

3. Final Answer:

   next() is called twice, causing navigation to fail -> Option D

4. Quick Check:

   Two next() calls in one guard = B [OK]

Hint: Call next() only once per guard to avoid errors [OK]

Common Mistakes:

• Calling next() multiple times in one guard
• Not returning after next('/login')
• Assuming meta is always defined

5. You want to protect a nested route /admin/settings so that only logged-in users can access it. You have a global beforeEach guard and a route-level beforeEnter guard on /admin. Which approach correctly ensures the user is redirected to /login if not logged in, without redundant checks?

hard

A. Check login only in global beforeEach; remove beforeEnter guard from /admin route

B. Check login only in beforeEnter guard on /admin; global beforeEach does not check login

C. Check login in both global beforeEach and beforeEnter guard on /admin

D. Do not check login in any guard; rely on component logic

Solution

1. Step 1: Understand guard execution order and redundancy

   Global beforeEach runs before every route, including nested ones. Route-level beforeEnter runs after global guards.

2. Step 2: Avoid redundant login checks

   Checking login in both guards causes duplicate redirects and complexity. Checking only in global guard covers all routes.

3. Final Answer:

   Check login only in global beforeEach; remove beforeEnter guard from /admin route -> Option A

4. Quick Check:

   Single global guard for login check avoids redundancy = A [OK]

Hint: Use global guard for login checks to avoid duplicate logic [OK]

Common Mistakes:

• Duplicating login checks in multiple guards
• Relying on component logic instead of guards
• Ignoring nested route guard order