Route parameters with useRoute in Vue - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What does this Vue component display when the route parameter 'id' is '42'?

Consider this Vue 3 component using useRoute to access route parameters.

import { defineComponent } from 'vue';
import { useRoute } from 'vue-router';

export default defineComponent({
  setup() {
    const route = useRoute();
    return { id: route.params.id };
  },
  template: `
User ID: {{ id }}
`
});

If the current route is /user/42 where id is a route param, what will be rendered?

Vue

import { defineComponent } from 'vue';
import { useRoute } from 'vue-router';

export default defineComponent({
  setup() {
    const route = useRoute();
    return { id: route.params.id };
  },
  template: `<div>User ID: {{ id }}</div>`
});

A <div>User ID: 42</div>

B <div>User ID: {{ id }}</div>

C <div>User ID: undefined</div>

D <div>User ID: </div>

💡 Hint

Remember that useRoute() gives access to the current route's parameters.

The useRoute() hook returns the current route object. Accessing route.params.id retrieves the 'id' parameter from the URL. If the URL is /user/42, then id is '42', so the component renders User ID: 42.

📝 Syntax

intermediate

Which option correctly accesses a nested route parameter 'postId' using useRoute?

Given a nested route with parameter postId, which code correctly extracts it inside setup()?

Vue

import { useRoute } from 'vue-router';

export default {
  setup() {
    // Which option correctly gets postId?
  }
}

A const route = useRoute; const postId = route.params.postId;

B const { postId } = useRoute.params;

C const route = useRoute(); const postId = route.params.postId;

D const postId = useRoute().params.postId;

💡 Hint

Remember useRoute is a function that returns the route object.

Option C correctly calls useRoute() to get the route object, then accesses params.postId. Option C tries to access params on the function itself, which is invalid. Option C calls useRoute() inline, which is valid but less clear. Option C assigns the function itself without calling it, so route.params is undefined.

❓ state_output

advanced

What is the value of 'userId' after route changes from '/user/1' to '/user/5' in this component?

Consider this Vue 3 component that uses useRoute and a watch to update userId:

import { ref, watch } from 'vue';
import { useRoute } from 'vue-router';

export default {
  setup() {
    const route = useRoute();
    const userId = ref(route.params.id);

    watch(() => route.params.id, (newId) => {
      userId.value = newId;
    });

    return { userId };
  }
};

If the route changes from /user/1 to /user/5, what will be the value of userId.value?

Vue

import { ref, watch } from 'vue';
import { useRoute } from 'vue-router';

export default {
  setup() {
    const route = useRoute();
    const userId = ref(route.params.id);

    watch(() => route.params.id, (newId) => {
      userId.value = newId;
    });

    return { userId };
  }
};

A 5

B 1

C undefined

D null

💡 Hint

The watch updates userId when the route param changes.

The watch listens for changes to route.params.id. When the route changes from '/user/1' to '/user/5', the watcher runs and updates userId.value to '5'.

🔧 Debug

advanced

Why does this component show 'undefined' for route param 'productId'?

Look at this Vue 3 component:

import { defineComponent } from 'vue';
import { useRoute } from 'vue-router';

export default defineComponent({
  setup() {
    const route = useRoute;
    return { productId: route.params.productId };
  },
  template: `
Product: {{ productId }}
`
});

When the route is /product/10, the component shows Product: undefined. Why?

Vue

import { defineComponent } from 'vue';
import { useRoute } from 'vue-router';

export default defineComponent({
  setup() {
    const route = useRoute;
    return { productId: route.params.productId };
  },
  template: `<div>Product: {{ productId }}</div>`
});

A Because productId is not defined in the route params.

B Because useRoute must be imported from 'vue' not 'vue-router'.

C Because the template syntax is incorrect and does not interpolate productId.

D Because useRoute is not called as a function, so route is the function itself, not the route object.

💡 Hint

Check how useRoute is used in setup().

The code assigns route = useRoute without calling it. So route is the function, not the route object. Accessing route.params is undefined, causing productId to be undefined.

🧠 Conceptual

expert

Which statement about useRoute and reactive route params is true?

Consider the following statements about useRoute in Vue Router:

1. useRoute() returns a reactive route object.
2. Route params accessed via useRoute().params are reactive and update automatically.
3. Directly destructuring params like const { id } = useRoute().params keeps id reactive.
4. Watching useRoute().params.id is the recommended way to react to param changes.

Which is the only true statement?

A Only statement 3 is true; destructuring keeps reactivity but useRoute is not reactive.

B Only statements 1 and 2 are true; destructuring breaks reactivity, and watching params.id is correct.

C All statements are true; destructuring keeps reactivity and watching params.id works fine.

D Only statement 4 is true; useRoute is not reactive but watching params.id works.

💡 Hint

Think about how destructuring affects reactivity in Vue.

useRoute() returns a reactive route object, so statements 1 and 2 are true. However, destructuring const { id } = useRoute().params breaks reactivity because it copies the value, so statement 3 is false. Watching useRoute().params.id is the recommended way to react to param changes, so statement 4 is true. But since statement 4 is true and 3 is false, only 1 and 2 are fully true together.

Practice

1. What does the useRoute function in Vue Router allow you to do inside a component?

easy

A. Access the current route's parameters and information

B. Change the URL path programmatically

C. Register a new route dynamically

D. Navigate to a different route without reloading

Solution

1. Step 1: Understand the purpose of useRoute

   useRoute is a Vue Router composable that provides access to the current route object inside a component.

2. Step 2: Identify what can be accessed with useRoute

   It allows reading route parameters, query, name, and path but does not change routes or register them.

3. Final Answer:

   Access the current route's parameters and information -> Option A

4. Quick Check:

   useRoute reads route info = B [OK]

Hint: useRoute reads route info, doesn't change or register routes [OK]

Common Mistakes:

• Thinking useRoute changes routes
• Confusing useRoute with useRouter
• Assuming useRoute registers routes

2. Which of the following is the correct way to import and use useRoute in a Vue 3 component's setup() function?

easy

A. import { useRoute } from 'vue-router'; const route = useRoute(route);

B. import useRoute from 'vue-router'; const route = useRoute();

C. import { useRoute } from 'vue-router'; const route = useRoute();

D. import { useRoute } from 'vue'; const route = useRoute();

Solution

1. Step 1: Check the import source

   useRoute is exported from 'vue-router', so import must be from 'vue-router'.

2. Step 2: Verify usage syntax

   The correct usage is calling useRoute() without arguments to get the current route object.

3. Final Answer:

   import { useRoute } from 'vue-router'; const route = useRoute(); -> Option C

4. Quick Check:

   Correct import and call = D [OK]

Hint: Import from 'vue-router' and call useRoute() with no arguments [OK]

Common Mistakes:

• Importing from 'vue' instead of 'vue-router'
• Calling useRoute with arguments
• Using default import instead of named import

3. Given this Vue 3 component code snippet, what will be logged when the URL is /user/42 and the route is defined as /user/:id?

import { useRoute } from 'vue-router';
import { onMounted } from 'vue';

export default {
  setup() {
    const route = useRoute();
    onMounted(() => {
      console.log(route.params.id);
    });
  }
}

medium

A. null

B. undefined

C. user

D. 42

Solution

1. Step 1: Identify the route parameter

   The route is defined as /user/:id, so id is a parameter expected in route.params.

2. Step 2: Check the URL and logged value

   The URL is /user/42, so route.params.id will be "42". The console logs this value on mount.

3. Final Answer:

   42 -> Option D

4. Quick Check:

   route.params.id = "42" [OK]

Hint: Route param matches URL segment after colon :id [OK]

Common Mistakes:

• Expecting param name instead of value
• Confusing params with query
• Logging before route is ready

4. What is the main issue with this Vue 3 component code that tries to react to route parameter changes?

import { useRoute } from 'vue-router';
import { computed } from 'vue';

export default {
  setup() {
    const route = useRoute();
    const userId = computed(() => route.params.id);
    return { userId };
  }
}

The component does not update userId when the route changes.

medium

A. The route object is not reactive, so computed won't update

B. The computed function is missing a dependency array

C. The useRoute hook must be called inside onMounted

D. The userId should be a ref, not computed

Solution

1. Step 1: Understand reactivity of route

   The route object returned by useRoute() is reactive, but its params property is not deeply reactive by default.

2. Step 2: Why computed does not update

   Because route.params is not reactive, the computed property does not track changes, so userId stays the same.

3. Final Answer:

   The route object is not reactive, so computed won't update -> Option A

4. Quick Check:

   Route params not reactive = A [OK]

Hint: Route params are not deeply reactive; watch route.fullPath instead [OK]

Common Mistakes:

• Assuming route.params is reactive
• Calling useRoute inside lifecycle hooks
• Using ref instead of computed incorrectly

5. You want to create a Vue 3 component that displays the user ID from the route parameter and updates automatically when the route changes. Which approach correctly achieves this?

import { useRoute } from 'vue-router';
import { computed, watch, ref } from 'vue';

export default {
  setup() {
    const route = useRoute();
    // What should userId be?
    const userId = ???
    return { userId };
  }
}

hard

A. computed(() => route.params.id)

B. computed(() => route.params.id) with a watch on route.fullPath to trigger updates

C. computed(() => route.fullPath.split('/')[2])

D. ref(route.params.id) without any watcher

Solution

1. Step 1: Understand reactivity limitations

   Route params are not deeply reactive, so computed(() => route.params.id) alone won't update when params change.

2. Step 2: Use a watch on route.fullPath to trigger updates

   Watching route.fullPath (which is reactive) and recomputing userId ensures updates when the route changes.

3. Final Answer:

   computed(() => route.params.id) with a watch on route.fullPath to trigger updates -> Option B

4. Quick Check:

   Watch route.fullPath for param changes = C [OK]

Hint: Watch route.fullPath to react to param changes in computed [OK]

Common Mistakes:

• Using computed alone without watch
• Parsing fullPath manually without reactivity
• Using ref without updating on route change