Component registration (global vs local) in Vue - Practice Questions

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when a locally registered component is used outside its parent?

Consider a Vue 3 app where ChildComp is registered locally inside ParentComp. What will happen if you try to use <ChildComp /> inside App.vue without registering it globally?

Vue

<script setup>
import ParentComp from './ParentComp.vue'
</script>
<template>
  <ParentComp />
  <ChildComp />
</template>

A The app will compile but <code>ChildComp</code> will render as plain text <code>&lt;ChildComp /&gt;</code>.

B Vue will render a blank space where <code>ChildComp</code> is used without errors.

C Vue will log a console warning: <code>Failed to resolve component: ChildComp</code>.

D The <code>ChildComp</code> will render normally because local registration is global by default.

💡 Hint

Think about where components are known and registered in Vue.

Locally registered components are only known inside the component where they are registered. Using them outside without global registration causes Vue to not recognize the tag, resulting in a console warning.

📝 Syntax

intermediate

Which option correctly registers a component globally in Vue 3?

You want to register MyButton globally so it can be used anywhere in your app without importing. Which code snippet does this correctly?

A app.component('MyButton', MyButton)

B app.use(MyButton)

C app.registerComponent('MyButton', MyButton)

D app.globalComponent('MyButton', MyButton)

💡 Hint

Look for the official Vue 3 method to register global components.

The app.component() method registers a component globally in Vue 3. Other options are not valid Vue API methods.

❓ state_output

advanced

What is the rendered output when a local component is registered with a different name?

Given this code, what will be rendered inside App.vue?

// ChildComp.vue
<template><div>Hello from Child</div></template>

// ParentComp.vue
<script setup>
import CustomChild from './ChildComp.vue'
</script>
<template>
  <CustomChild />
</template>

// App.vue
<template>
  <ParentComp />
</template>

A Nothing renders because the component name is mismatched

B <customchild></customchild>

C Runtime error: Unknown custom element <CustomChild>

D <div>Hello from Child</div>

💡 Hint

Check how local registration names affect usage inside the same component.

Inside ParentComp, the component is registered as CustomChild and used as such, so it renders correctly. The name change only affects usage inside ParentComp.

🔧 Debug

advanced

Why does this globally registered component fail to render?

You registered MyWidget globally but when you use <my-widget /> in your template, nothing shows. Why?

const app = createApp(App)
app.component('MyWidget', MyWidget)
app.mount('#app')

A Vue automatically converts PascalCase to kebab-case, so <code>&lt;my-widget /&gt;</code> should work; issue is elsewhere.

B Component names are case-sensitive; use <code>&lt;MyWidget /&gt;</code> instead of kebab-case.

C You must register components in kebab-case strings to use kebab-case tags.

D The component must be imported with a .vue extension to render.

💡 Hint

Think about Vue's handling of component names in templates.

Vue automatically converts PascalCase component names to kebab-case in templates, so <my-widget /> is valid for 'MyWidget'. The problem is likely elsewhere, such as the component code or mounting.

🧠 Conceptual

expert

Why prefer local registration over global in large Vue apps?

In a large Vue 3 app, why is local component registration often preferred over global registration?

A Local registration allows components to be used anywhere without importing, reducing code size.

B Local registration improves app startup time by loading only needed components per view.

C Global registration causes components to lose reactivity and state management features.

D Global registration automatically scopes CSS which can cause style conflicts.

💡 Hint

Think about performance and code organization in big apps.

Local registration helps keep the app lightweight by only loading components where needed, improving startup time and maintainability. Global registration loads all components upfront, which can slow down the app.

Practice

1. What is the main difference between global and local component registration in Vue?

easy

A. Global registration requires importing components manually, local does not.

B. Local registration makes a component available everywhere, global limits it to one component.

C. Global registration makes a component available everywhere, local limits it to one component.

D. Local registration automatically registers components globally.

Solution

1. Step 1: Understand global registration

   Global registration means the component can be used in any template without importing it again.

2. Step 2: Understand local registration

   Local registration means the component is only available inside the component where it is registered.

3. Final Answer:

   Global registration makes a component available everywhere, local limits it to one component. -> Option C

4. Quick Check:

   Global = everywhere, Local = one component [OK]

Hint: Global = everywhere, local = one place only [OK]

Common Mistakes:

• Confusing global with local availability
• Thinking local registration is automatic
• Assuming global requires manual import every time

2. Which of the following is the correct syntax to register a component locally inside a Vue component?

easy

A. export default { globalComponents: { MyComponent } }

B. Vue.component('MyComponent', MyComponent)

C. import MyComponent from './MyComponent.vue';

D. components: { MyComponent }

Solution

1. Step 1: Identify local registration syntax

   Local registration uses the components option inside the component definition object.

2. Step 2: Match correct syntax

   The syntax is components: { MyComponent } to register locally.

3. Final Answer:

   components: { MyComponent } -> Option D

4. Quick Check:

   Local registration uses components: { } [OK]

Hint: Local registration uses components: { ComponentName } [OK]

Common Mistakes:

• Using Vue.component() for local registration
• Confusing import statement with registration
• Trying to use globalComponents option which doesn't exist

3. Given this code, what will be the output when rendering <ParentComponent/>?

const ChildComponent = {
  template: '
Child here
'
}

const ParentComponent = {
  template: '
',
  components: { ChildComponent }
}

app.component('parent-component', ParentComponent)
app.mount('#app')

medium

A. Child here

B. Error: Unknown custom element

C.

D. Child here

Solution

1. Step 1: Check local registration in ParentComponent

   ChildComponent is registered locally inside ParentComponent using components: { ChildComponent }.

2. Step 2: Understand template rendering

   The tag inside ParentComponent's template will render ChildComponent's template

   Child here

   only if the tag name matches the registered component name in kebab-case.

3. Step 3: Identify the issue

   The component is registered as ChildComponent but used as , which Vue treats as a different tag. Since 'child-component' is not globally registered, Vue will throw an unknown custom element error.

4. Final Answer:

   Error: Unknown custom element <child-component> -> Option B

5. Quick Check:

   Component names are case-sensitive and must match usage [OK]

Hint: Component names must match tag names exactly or use kebab-case [OK]

Common Mistakes:

• Assuming PascalCase component names automatically match kebab-case tags
• Forgetting to register components globally when using kebab-case tags
• Expecting local registration to work with mismatched tag names

4. What is wrong with this Vue code snippet?

const app = Vue.createApp({})

app.component('MyButton', {
  template: 'Click me'
})

const AnotherComponent = {
  template: ''
}

app.component('AnotherComponent', AnotherComponent)

app.mount('#app')

medium

A. The tag inside AnotherComponent template should be lowercase .

B. MyButton component is not registered globally.

C. AnotherComponent is missing local registration of MyButton.

D. Vue.createApp() cannot register components.

Solution

1. Step 1: Check component registration

   MyButton is registered globally using app.component('MyButton', ...), so it is available everywhere.

2. Step 2: Check template tag casing

   Vue requires component tags in templates to be kebab-case or PascalCase but HTML is case-insensitive, so should be .

3. Final Answer:

   The <MyButton /> tag inside AnotherComponent template should be lowercase <my-button />. -> Option A

4. Quick Check:

   Component tags must be kebab-case in templates [OK]

Hint: Use kebab-case for component tags in templates [OK]

Common Mistakes:

• Using PascalCase tags directly in templates
• Thinking global registration needs import in every component
• Assuming Vue.createApp() can't register components

5. You have a button component used in many places and a modal component used only inside one page component. How should you register them for best practice?

hard

A. Register the button component globally and the modal component locally inside the page component.

B. Register both components globally for consistency.

C. Register both components locally inside each component that uses them.

D. Register the modal component globally and the button component locally.

Solution

1. Step 1: Consider usage frequency

   The button is used many places, so global registration avoids repeated imports and registrations.

2. Step 2: Consider component scope

   The modal is used only inside one page component, so local registration keeps scope limited and reduces global clutter.

3. Final Answer:

   Register the button component globally and the modal component locally inside the page component. -> Option A

4. Quick Check:

   Global for many uses, local for few uses [OK]

Hint: Global for shared, local for limited use components [OK]

Common Mistakes:

• Registering rarely used components globally unnecessarily
• Registering widely used components locally repeatedly
• Ignoring app size and performance considerations