Vue.js • Chapter 25 • Foundations to Advanced
Composition API vs Options API
Each topic includes substantial explanation, ten focused examples, its own Vue code example, step-by-step reasoning, expected behavior, and practice.
25.1 Choosing an API Style
Choosing an API Style is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 25, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Choosing an API Style in Chapter 25, 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 Choosing an API Style to composition api vs options api. 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
Choosing an API Style is a focused part of Vue application design in Chapter 25. 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 Choosing an API Style. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Choosing an API Style is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 25, topic 1.
Example 2: Change one reactive value
Change one value involved in Choosing an API Style 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 Choosing an API Style 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 Choosing an API Style edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Choosing an API Style in the quiz screen while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Choosing an API Style is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 25, topic 1.
Example 6: State ownership review
Remove duplicated state from the analytics view. For Choosing an API Style, 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 Choosing an API Style. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Choosing an API Style 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 Choosing an API Style. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Choosing an API Style in the search panel for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Choosing an API Style is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 25, topic 1.
Vue code example
<script setup>
import { ref } from 'vue'
const topic = "Choosing an API Style"
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 Choosing an API Style.
- 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 Choosing an API Style and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Choosing an API Style from Chapter 25. 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.
25.2 Organizing by Feature
Organizing by Feature is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 25, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Organizing by Feature in Chapter 25, 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 Organizing by Feature to composition api vs options api. 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
Organizing by Feature is a focused part of Vue application design in Chapter 25. 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 Organizing by Feature. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Organizing by Feature is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 25, topic 2.
Example 2: Change one reactive value
Change one value involved in Organizing by Feature 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 Organizing by Feature 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 Organizing by Feature edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Organizing by Feature in the course dashboard while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Organizing by Feature is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 25, topic 2.
Example 6: State ownership review
Remove duplicated state from the profile editor. For Organizing by Feature, 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 Organizing by Feature. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Organizing by Feature 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 Organizing by Feature. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Organizing by Feature in the booking form for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Organizing by Feature is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 25, topic 2.
Vue code example
<script setup>
import { ref } from 'vue'
const topic = "Organizing by Feature"
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 Organizing by Feature.
- 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 Organizing by Feature and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Organizing by Feature from Chapter 25. 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.
25.3 Reusing Logic
Reusing Logic is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 25, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Reusing Logic in Chapter 25, 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 Reusing Logic to composition api vs options api. 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
Reusing Logic is a focused part of Vue application design in Chapter 25. 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 Reusing Logic. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Reusing Logic is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 25, topic 3.
Example 2: Change one reactive value
Change one value involved in Reusing Logic 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 Reusing Logic 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 Reusing Logic edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Reusing Logic in the shopping cart while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Reusing Logic is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 25, topic 3.
Example 6: State ownership review
Remove duplicated state from the lesson tracker. For Reusing Logic, 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 Reusing Logic. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Reusing Logic 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 Reusing Logic. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Reusing Logic in the photo gallery for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Reusing Logic is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 25, topic 3.
Vue code example
<script setup>
import { ref } from 'vue'
const topic = "Reusing Logic"
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 Reusing Logic.
- 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 Reusing Logic and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Reusing Logic from Chapter 25. 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.
25.4 Team Consistency
Team Consistency is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 25, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Team Consistency in Chapter 25, 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 Team Consistency to composition api vs options api. 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
Team Consistency is a focused part of Vue application design in Chapter 25. 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 search panel that demonstrates Team Consistency. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Team Consistency is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 25, topic 4.
Example 2: Change one reactive value
Change one value involved in Team Consistency 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 Team Consistency 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 Team Consistency edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Team Consistency in the message panel while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Team Consistency is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 25, topic 4.
Example 6: State ownership review
Remove duplicated state from the admin table. For Team Consistency, 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 Team Consistency. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Team Consistency 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 Team Consistency. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Team Consistency in the language selector for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Team Consistency is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 25, topic 4.
Vue code example
<script setup>
import { ref } from 'vue'
const topic = "Team Consistency"
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 Team Consistency.
- 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 Team Consistency and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Team Consistency from Chapter 25. 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.
25.5 Migrating Between Styles
Migrating Between Styles is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 25, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Migrating Between Styles in Chapter 25, 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 Migrating Between Styles to composition api vs options api. 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
Migrating Between Styles is a focused part of Vue application design in Chapter 25. 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 Migrating Between Styles. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Migrating Between Styles is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 25, topic 5.
Example 2: Change one reactive value
Change one value involved in Migrating Between Styles 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 Migrating Between Styles 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 Migrating Between Styles edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Migrating Between Styles in the notification center while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Migrating Between Styles is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 25, topic 5.
Example 6: State ownership review
Remove duplicated state from the task board. For Migrating Between Styles, 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 Migrating Between Styles. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Migrating Between Styles 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 Migrating Between Styles. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Migrating Between Styles in the support form for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Migrating Between Styles is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 25, topic 5.
Vue code example
<script setup>
import { ref } from 'vue'
const topic = "Migrating Between Styles"
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 Migrating Between Styles.
- 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 Migrating Between Styles and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Migrating Between Styles from Chapter 25. 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 25 review — 10 questions and answers
1. What is the purpose of Choosing an API Style?
Answer: Choosing an API Style is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
2. What should you inspect when Choosing an API Style 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 Organizing by Feature?
Answer: Organizing by Feature is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
4. What should you inspect when Organizing by Feature 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 Reusing Logic?
Answer: Reusing Logic is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
6. What should you inspect when Reusing Logic 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 Team Consistency?
Answer: Team Consistency is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
8. What should you inspect when Team Consistency 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 Migrating Between Styles?
Answer: Migrating Between Styles is a focused part of Vue application design in Chapter 25. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
10. What should you inspect when Migrating Between Styles 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.