Component registration (global vs local) in Vue - Hands-On Comparison

Component registration (global vs local)

📖 Scenario: You are building a simple Vue app that shows a greeting message using a reusable component.You will learn how to register a component globally and locally in Vue 3.

🎯 Goal: Create a Vue app with a GreetingMessage component.First, register the component globally so it can be used anywhere.Then, register the component locally inside the main app component.

📋 What You'll Learn

Create a GreetingMessage component that displays 'Hello, Vue learner!'

Register GreetingMessage globally using app.component()

Register GreetingMessage locally inside the main app component's components option

Use the GreetingMessage component in the main app template

💡 Why This Matters

🌍 Real World

In real Vue apps, components can be registered globally to reuse them everywhere or locally to keep scope limited and improve performance.

💼 Career

Understanding component registration is essential for building scalable Vue applications and collaborating with teams on component structure.

1

Create the GreetingMessage component

Create a Vue component called GreetingMessage using defineComponent. It should render a <p> tag with the text 'Hello, Vue learner!'.

Vue

// Create the GreetingMessage component using defineComponent
// Your code here

Hint

Use defineComponent and return a render function that creates a <p> element with the greeting text.

2

Register GreetingMessage globally

Create a Vue app using createApp. Register the GreetingMessage component globally using app.component('GreetingMessage', GreetingMessage).

Vue

import { createApp } from 'vue';

// Create the app
// Register GreetingMessage globally
// Your code here

Hint

Use createApp({}) to create the app instance, then call app.component to register globally.

3

Register GreetingMessage locally in the main app component

Modify the main app component to register GreetingMessage locally inside the components option.

Vue

const app = createApp({
  // Register GreetingMessage locally here
  // Your code here
});
app.component('GreetingMessage', GreetingMessage);

Hint

Inside createApp, add a components object with GreetingMessage as a property.

4

Use GreetingMessage component in the app template

Add a template option to the main app component that uses the <GreetingMessage /> tag to display the greeting.

Vue

const app = createApp({
  components: {
    GreetingMessage
  },
  // Add template using 
  // Your code here
});
app.component('GreetingMessage', GreetingMessage);

Hint

Add a template string with the <GreetingMessage /> tag inside the app component.

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