Vue.js • Chapter 34 • Foundations to Advanced
Plugins
Each topic includes substantial explanation, ten focused examples, its own Vue code example, step-by-step reasoning, expected behavior, and practice.
34.1 Creating a Plugin
Creating a Plugin is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 34, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Creating a Plugin in Chapter 34, inspect reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Keep writable state ownership explicit, derive values when possible, and separate display calculations from network, DOM, storage, timer, or other external work.
This lesson connects Creating a Plugin to plugins. Start with one working case, verify the expected output, then add one edge case and explain what Vue tracks, reuses, creates, removes, or updates.
Concept in plain language
Creating a Plugin is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
10 teaching examples
Example 1: Smallest useful case
Build the smallest photo gallery that demonstrates Creating a Plugin. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Creating a Plugin is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 34, topic 1.
Example 2: Change one reactive value
Change one value involved in Creating a Plugin inside the notification center. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use Creating a Plugin across two components in the task board. Compare which component owns the writable data and which component only receives or presents it.
Example 4: Edge case
Add an empty, missing, invalid, delayed, or rapidly changing value to the language selector. Handle the Creating a Plugin edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Creating a Plugin in the quiz screen while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Creating a Plugin is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 34, topic 1.
Example 6: State ownership review
Remove duplicated state from the analytics view. For Creating a Plugin, derive values when possible and keep the writable source with the component or store that owns it.
Example 7: Slow-network scenario
Assume the support form has a slow request while using Creating a Plugin. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Creating a Plugin responsibility from a crowded course dashboard into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the profile editor before optimizing Creating a Plugin. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Creating a Plugin in the search panel for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Creating a Plugin is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 34, topic 1.
Vue code example
export const analyticsPlugin = {
install(app){ app.provide('analytics',{ track:event=>console.log(event) }) }
}Step-by-step code explanation
- Identify the Vue responsibility demonstrated by Creating a Plugin.
- Read the reactive state, props, route/store input, or injected value before the template.
- Trace the event, dependency, watcher, lifecycle hook, or navigation action that changes the display.
- Test one normal path and one edge case, including cleanup when external work is involved.
- Confirm accessibility, mobile width, and RTL behavior for user-facing controls and translated text.
Expected behavior: A small Vue interface demonstrates Creating a Plugin and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Creating a Plugin from Chapter 34. Predict the result before running it, test one edge case, and explain which reactive value, prop, event, route, store, or lifecycle step caused the update. Then check accessibility, narrow-screen width, and RTL behavior where relevant.
34.2 app.use
app.use is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 34, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For app.use in Chapter 34, inspect reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Keep writable state ownership explicit, derive values when possible, and separate display calculations from network, DOM, storage, timer, or other external work.
This lesson connects app.use to plugins. Start with one working case, verify the expected output, then add one edge case and explain what Vue tracks, reuses, creates, removes, or updates.
Concept in plain language
app.use is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
10 teaching examples
Example 1: Smallest useful case
Build the smallest language selector that demonstrates app.use. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. app.use is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 34, topic 2.
Example 2: Change one reactive value
Change one value involved in app.use inside the quiz screen. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use app.use across two components in the analytics view. Compare which component owns the writable data and which component only receives or presents it.
Example 4: Edge case
Add an empty, missing, invalid, delayed, or rapidly changing value to the support form. Handle the app.use edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use app.use in the course dashboard while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. app.use is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 34, topic 2.
Example 6: State ownership review
Remove duplicated state from the profile editor. For app.use, derive values when possible and keep the writable source with the component or store that owns it.
Example 7: Slow-network scenario
Assume the search panel has a slow request while using app.use. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the app.use responsibility from a crowded shopping cart into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the lesson tracker before optimizing app.use. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review app.use in the booking form for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. app.use is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 34, topic 2.
Vue code example
<script setup>
import { ref } from 'vue'
const topic = "app.use"
const active = ref(false)
</script>
<template>
<section><h2>{{ topic }}</h2><button :aria-pressed="active" @click="active=!active">Toggle state</button><p>{{ active ? 'Active' : 'Inactive' }}</p></section>
</template>Step-by-step code explanation
- Identify the Vue responsibility demonstrated by app.use.
- Read the reactive state, props, route/store input, or injected value before the template.
- Trace the event, dependency, watcher, lifecycle hook, or navigation action that changes the display.
- Test one normal path and one edge case, including cleanup when external work is involved.
- Confirm accessibility, mobile width, and RTL behavior for user-facing controls and translated text.
Expected behavior: A small Vue interface demonstrates app.use and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on app.use from Chapter 34. Predict the result before running it, test one edge case, and explain which reactive value, prop, event, route, store, or lifecycle step caused the update. Then check accessibility, narrow-screen width, and RTL behavior where relevant.
34.3 Global Properties
Global Properties is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 34, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Global Properties in Chapter 34, inspect component ownership, data direction, event payloads, and the public component contract. Keep writable state ownership explicit, derive values when possible, and separate display calculations from network, DOM, storage, timer, or other external work.
This lesson connects Global Properties to plugins. Start with one working case, verify the expected output, then add one edge case and explain what Vue tracks, reuses, creates, removes, or updates.
Concept in plain language
Global Properties is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
10 teaching examples
Example 1: Smallest useful case
Build the smallest support form that demonstrates Global Properties. Keep one input and one visible result, then explain component ownership, data direction, event payloads, and the public component contract. Global Properties is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 34, topic 3.
Example 2: Change one reactive value
Change one value involved in Global Properties inside the course dashboard. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use Global Properties across two components in the profile editor. Compare which component owns the writable data and which component only receives or presents it.
Example 4: Edge case
Add an empty, missing, invalid, delayed, or rapidly changing value to the search panel. Handle the Global Properties edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Global Properties in the shopping cart while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Global Properties is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 34, topic 3.
Example 6: State ownership review
Remove duplicated state from the lesson tracker. For Global Properties, derive values when possible and keep the writable source with the component or store that owns it.
Example 7: Slow-network scenario
Assume the booking form has a slow request while using Global Properties. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Global Properties responsibility from a crowded message panel into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the admin table before optimizing Global Properties. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Global Properties in the photo gallery for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Global Properties is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 34, topic 3.
Vue code example
<script setup>
defineProps({ title: { type: String, required: true }, active: Boolean })
</script>
<template><article :class="{ active }"><h2>{{ title }}</h2></article></template>Step-by-step code explanation
- Identify the Vue responsibility demonstrated by Global Properties.
- Read the reactive state, props, route/store input, or injected value before the template.
- Trace the event, dependency, watcher, lifecycle hook, or navigation action that changes the display.
- Test one normal path and one edge case, including cleanup when external work is involved.
- Confirm accessibility, mobile width, and RTL behavior for user-facing controls and translated text.
Expected behavior: A small Vue interface demonstrates Global Properties and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Global Properties from Chapter 34. Predict the result before running it, test one edge case, and explain which reactive value, prop, event, route, store, or lifecycle step caused the update. Then check accessibility, narrow-screen width, and RTL behavior where relevant.
34.4 Provide from Plugins
provide exposes a value to descendants without passing the same prop through every intermediate component. In Chapter 34, apply this definition specifically to Provide from Plugins and trace how it changes the rendered interface. In Chapter 34, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Provide from Plugins in Chapter 34, inspect reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Keep writable state ownership explicit, derive values when possible, and separate display calculations from network, DOM, storage, timer, or other external work.
This lesson connects Provide from Plugins to plugins. Start with one working case, verify the expected output, then add one edge case and explain what Vue tracks, reuses, creates, removes, or updates.
Concept in plain language
provide exposes a value to descendants without passing the same prop through every intermediate component. In Chapter 34, apply this definition specifically to Provide from Plugins and trace how it changes the rendered interface.
10 teaching examples
Example 1: Smallest useful case
Build the smallest search panel that demonstrates Provide from Plugins. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. provide exposes a value to descendants without passing the same prop through every intermediate component. In Chapter 34, apply this definition specifically to Provide from Plugins and trace how it changes the rendered interface. This is example 1 for Chapter 34, topic 4.
Example 2: Change one reactive value
Change one value involved in Provide from Plugins inside the shopping cart. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use Provide from Plugins across two components in the lesson tracker. Compare which component owns the writable data and which component only receives or presents it.
Example 4: Edge case
Add an empty, missing, invalid, delayed, or rapidly changing value to the booking form. Handle the Provide from Plugins edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Provide from Plugins in the message panel while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. provide exposes a value to descendants without passing the same prop through every intermediate component. In Chapter 34, apply this definition specifically to Provide from Plugins and trace how it changes the rendered interface. This is example 5 for Chapter 34, topic 4.
Example 6: State ownership review
Remove duplicated state from the admin table. For Provide from Plugins, derive values when possible and keep the writable source with the component or store that owns it.
Example 7: Slow-network scenario
Assume the photo gallery has a slow request while using Provide from Plugins. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Provide from Plugins responsibility from a crowded notification center into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the task board before optimizing Provide from Plugins. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Provide from Plugins in the language selector for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. provide exposes a value to descendants without passing the same prop through every intermediate component. In Chapter 34, apply this definition specifically to Provide from Plugins and trace how it changes the rendered interface. This is example 10 for Chapter 34, topic 4.
Vue code example
export const analyticsPlugin = {
install(app){ app.provide('analytics',{ track:event=>console.log(event) }) }
}Step-by-step code explanation
- Identify the Vue responsibility demonstrated by Provide from Plugins.
- Read the reactive state, props, route/store input, or injected value before the template.
- Trace the event, dependency, watcher, lifecycle hook, or navigation action that changes the display.
- Test one normal path and one edge case, including cleanup when external work is involved.
- Confirm accessibility, mobile width, and RTL behavior for user-facing controls and translated text.
Expected behavior: A small Vue interface demonstrates Provide from Plugins and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Provide from Plugins from Chapter 34. Predict the result before running it, test one edge case, and explain which reactive value, prop, event, route, store, or lifecycle step caused the update. Then check accessibility, narrow-screen width, and RTL behavior where relevant.
34.5 Plugin Design Boundaries
Plugin Design Boundaries is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 34, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Plugin Design Boundaries in Chapter 34, inspect reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Keep writable state ownership explicit, derive values when possible, and separate display calculations from network, DOM, storage, timer, or other external work.
This lesson connects Plugin Design Boundaries to plugins. Start with one working case, verify the expected output, then add one edge case and explain what Vue tracks, reuses, creates, removes, or updates.
Concept in plain language
Plugin Design Boundaries is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
10 teaching examples
Example 1: Smallest useful case
Build the smallest booking form that demonstrates Plugin Design Boundaries. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Plugin Design Boundaries is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 34, topic 5.
Example 2: Change one reactive value
Change one value involved in Plugin Design Boundaries inside the message panel. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use Plugin Design Boundaries across two components in the admin table. Compare which component owns the writable data and which component only receives or presents it.
Example 4: Edge case
Add an empty, missing, invalid, delayed, or rapidly changing value to the photo gallery. Handle the Plugin Design Boundaries edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Plugin Design Boundaries in the notification center while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Plugin Design Boundaries is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 34, topic 5.
Example 6: State ownership review
Remove duplicated state from the task board. For Plugin Design Boundaries, derive values when possible and keep the writable source with the component or store that owns it.
Example 7: Slow-network scenario
Assume the language selector has a slow request while using Plugin Design Boundaries. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Plugin Design Boundaries responsibility from a crowded quiz screen into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the analytics view before optimizing Plugin Design Boundaries. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Plugin Design Boundaries in the support form for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Plugin Design Boundaries is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 34, topic 5.
Vue code example
export const analyticsPlugin = {
install(app){ app.provide('analytics',{ track:event=>console.log(event) }) }
}Step-by-step code explanation
- Identify the Vue responsibility demonstrated by Plugin Design Boundaries.
- Read the reactive state, props, route/store input, or injected value before the template.
- Trace the event, dependency, watcher, lifecycle hook, or navigation action that changes the display.
- Test one normal path and one edge case, including cleanup when external work is involved.
- Confirm accessibility, mobile width, and RTL behavior for user-facing controls and translated text.
Expected behavior: A small Vue interface demonstrates Plugin Design Boundaries and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Plugin Design Boundaries from Chapter 34. Predict the result before running it, test one edge case, and explain which reactive value, prop, event, route, store, or lifecycle step caused the update. Then check accessibility, narrow-screen width, and RTL behavior where relevant.
Chapter 34 review — 10 questions and answers
1. What is the purpose of Creating a Plugin?
Answer: Creating a Plugin is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
2. What should you inspect when Creating a Plugin behaves unexpectedly?
Answer: Inspect reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Reduce the feature to a small component and trace reactive input through the rendered result.
3. What is the purpose of app.use?
Answer: app.use is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
4. What should you inspect when app.use behaves unexpectedly?
Answer: Inspect reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Reduce the feature to a small component and trace reactive input through the rendered result.
5. What is the purpose of Global Properties?
Answer: Global Properties is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
6. What should you inspect when Global Properties behaves unexpectedly?
Answer: Inspect component ownership, data direction, event payloads, and the public component contract. Reduce the feature to a small component and trace reactive input through the rendered result.
7. What is the purpose of Provide from Plugins?
Answer: provide exposes a value to descendants without passing the same prop through every intermediate component. In Chapter 34, apply this definition specifically to Provide from Plugins and trace how it changes the rendered interface.
8. What should you inspect when Provide from Plugins behaves unexpectedly?
Answer: Inspect reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Reduce the feature to a small component and trace reactive input through the rendered result.
9. What is the purpose of Plugin Design Boundaries?
Answer: Plugin Design Boundaries is a focused part of Vue application design in Chapter 34. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
10. What should you inspect when Plugin Design Boundaries behaves unexpectedly?
Answer: Inspect reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Reduce the feature to a small component and trace reactive input through the rendered result.