Vue.js • Chapter 48 • Foundations to Advanced
Code Splitting and Lazy Loading
Each topic includes substantial explanation, ten focused examples, its own Vue code example, step-by-step reasoning, expected behavior, and practice.
48.1 Dynamic Imports
Dynamic Imports is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 48, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Dynamic Imports in Chapter 48, 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 Dynamic Imports to code splitting and lazy loading. 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
Dynamic Imports is a focused part of Vue application design in Chapter 48. 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 shopping cart that demonstrates Dynamic Imports. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Dynamic Imports is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 48, topic 1.
Example 2: Change one reactive value
Change one value involved in Dynamic Imports inside the lesson tracker. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use Dynamic Imports across two components in the booking form. 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 message panel. Handle the Dynamic Imports edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Dynamic Imports in the admin table while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Dynamic Imports is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 48, topic 1.
Example 6: State ownership review
Remove duplicated state from the photo gallery. For Dynamic Imports, derive values when possible and keep the writable source with the component or store that owns it.
Example 7: Slow-network scenario
Assume the notification center has a slow request while using Dynamic Imports. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Dynamic Imports responsibility from a crowded task board into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the language selector before optimizing Dynamic Imports. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Dynamic Imports in the quiz screen for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Dynamic Imports is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 48, topic 1.
Vue code example
<script setup>
import { ref } from 'vue'
const topic = "Dynamic Imports"
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 Dynamic Imports.
- 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 Dynamic Imports and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Dynamic Imports from Chapter 48. 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.
48.2 Lazy Routes
Lazy Routes is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 48, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Lazy Routes in Chapter 48, inspect URL state, route parameters, matched records, navigation lifecycle, and failure states. 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 Lazy Routes to code splitting and lazy loading. 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
Lazy Routes is a focused part of Vue application design in Chapter 48. 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 message panel that demonstrates Lazy Routes. Keep one input and one visible result, then explain URL state, route parameters, matched records, navigation lifecycle, and failure states. Lazy Routes is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 48, topic 2.
Example 2: Change one reactive value
Change one value involved in Lazy Routes inside the admin table. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use Lazy Routes across two components in the photo gallery. 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 notification center. Handle the Lazy Routes edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Lazy Routes in the task board while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Lazy Routes is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 48, topic 2.
Example 6: State ownership review
Remove duplicated state from the language selector. For Lazy Routes, derive values when possible and keep the writable source with the component or store that owns it.
Example 7: Slow-network scenario
Assume the quiz screen has a slow request while using Lazy Routes. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Lazy Routes responsibility from a crowded analytics view into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the support form before optimizing Lazy Routes. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Lazy Routes in the course dashboard for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Lazy Routes is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 48, topic 2.
Vue code example
<script setup>
import { useRoute, useRouter } from 'vue-router'
const route = useRoute()
const router = useRouter()
function goHome(){ router.push('/') }
</script>
<template><p>Route: {{ route.fullPath }}</p><button @click="goHome">Home</button></template>Step-by-step code explanation
- Identify the Vue responsibility demonstrated by Lazy Routes.
- 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 Lazy Routes and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Lazy Routes from Chapter 48. 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.
48.3 Async Components
Async Components is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 48, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Async Components in Chapter 48, 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 Async Components to code splitting and lazy loading. 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
Async Components is a focused part of Vue application design in Chapter 48. 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 notification center that demonstrates Async Components. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Async Components is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 48, topic 3.
Example 2: Change one reactive value
Change one value involved in Async Components inside the task board. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use Async Components across two components in the language selector. 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 quiz screen. Handle the Async Components edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Async Components in the analytics view while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Async Components is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 48, topic 3.
Example 6: State ownership review
Remove duplicated state from the support form. For Async Components, derive values when possible and keep the writable source with the component or store that owns it.
Example 7: Slow-network scenario
Assume the course dashboard has a slow request while using Async Components. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Async Components responsibility from a crowded profile editor into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the search panel before optimizing Async Components. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Async Components in the shopping cart for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Async Components is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 48, topic 3.
Vue code example
import { defineAsyncComponent } from 'vue'
export const ReportsPanel = defineAsyncComponent(() => import('./ReportsPanel.vue'))Step-by-step code explanation
- Identify the Vue responsibility demonstrated by Async Components.
- 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 Async Components and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Async Components from Chapter 48. 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.
48.4 Chunk Boundaries
Chunk Boundaries is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 48, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Chunk Boundaries in Chapter 48, 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 Chunk Boundaries to code splitting and lazy loading. 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
Chunk Boundaries is a focused part of Vue application design in Chapter 48. 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 quiz screen that demonstrates Chunk Boundaries. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Chunk Boundaries is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 48, topic 4.
Example 2: Change one reactive value
Change one value involved in Chunk Boundaries inside the analytics view. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use Chunk Boundaries across two components in the support form. 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 course dashboard. Handle the Chunk Boundaries edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Chunk Boundaries in the profile editor while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Chunk Boundaries is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 48, topic 4.
Example 6: State ownership review
Remove duplicated state from the search panel. For Chunk 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 shopping cart has a slow request while using Chunk Boundaries. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Chunk Boundaries responsibility from a crowded lesson tracker into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the booking form before optimizing Chunk Boundaries. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Chunk Boundaries in the message panel for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Chunk Boundaries is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 48, topic 4.
Vue code example
<script setup>
import { ref } from 'vue'
const topic = "Chunk Boundaries"
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 Chunk 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 Chunk Boundaries and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Chunk Boundaries from Chapter 48. 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.
48.5 Loading Failures
Loading Failures is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 48, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Loading Failures in Chapter 48, 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 Loading Failures to code splitting and lazy loading. 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
Loading Failures is a focused part of Vue application design in Chapter 48. 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 course dashboard that demonstrates Loading Failures. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Loading Failures is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 48, topic 5.
Example 2: Change one reactive value
Change one value involved in Loading Failures inside the profile editor. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use Loading Failures across two components in the search panel. 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 shopping cart. Handle the Loading Failures edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Loading Failures in the lesson tracker while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Loading Failures is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 48, topic 5.
Example 6: State ownership review
Remove duplicated state from the booking form. For Loading Failures, derive values when possible and keep the writable source with the component or store that owns it.
Example 7: Slow-network scenario
Assume the message panel has a slow request while using Loading Failures. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Loading Failures responsibility from a crowded admin table into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the photo gallery before optimizing Loading Failures. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Loading Failures in the notification center for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Loading Failures is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 48, topic 5.
Vue code example
<script setup>
import { ref } from 'vue'
const topic = "Loading Failures"
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 Loading Failures.
- 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 Loading Failures and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Loading Failures from Chapter 48. 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 48 review — 10 questions and answers
1. What is the purpose of Dynamic Imports?
Answer: Dynamic Imports is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
2. What should you inspect when Dynamic Imports 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 Lazy Routes?
Answer: Lazy Routes is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
4. What should you inspect when Lazy Routes behaves unexpectedly?
Answer: Inspect URL state, route parameters, matched records, navigation lifecycle, and failure states. Reduce the feature to a small component and trace reactive input through the rendered result.
5. What is the purpose of Async Components?
Answer: Async Components is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
6. What should you inspect when Async Components 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.
7. What is the purpose of Chunk Boundaries?
Answer: Chunk Boundaries is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
8. What should you inspect when Chunk 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.
9. What is the purpose of Loading Failures?
Answer: Loading Failures is a focused part of Vue application design in Chapter 48. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
10. What should you inspect when Loading Failures 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.