Vue.js • Chapter 2 • Foundations to Advanced
JavaScript Essentials for Vue
Each topic includes substantial explanation, ten focused examples, its own Vue code example, step-by-step reasoning, expected behavior, and practice.
2.1 Variables Objects and Arrays
Variables Objects and Arrays is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 2, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Variables Objects and Arrays in Chapter 2, 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 Variables Objects and Arrays to javascript essentials for vue. 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
Variables Objects and Arrays is a focused part of Vue application design in Chapter 2. 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 analytics view that demonstrates Variables Objects and Arrays. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Variables Objects and Arrays is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 2, topic 1.
Example 2: Change one reactive value
Change one value involved in Variables Objects and Arrays inside the support form. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use Variables Objects and Arrays across two components in the course dashboard. 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 profile editor. Handle the Variables Objects and Arrays edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Variables Objects and Arrays in the search panel while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Variables Objects and Arrays is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 2, topic 1.
Example 6: State ownership review
Remove duplicated state from the shopping cart. For Variables Objects and Arrays, derive values when possible and keep the writable source with the component or store that owns it.
Example 7: Slow-network scenario
Assume the lesson tracker has a slow request while using Variables Objects and Arrays. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Variables Objects and Arrays responsibility from a crowded booking form into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the message panel before optimizing Variables Objects and Arrays. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Variables Objects and Arrays in the admin table for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Variables Objects and Arrays is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 2, topic 1.
Vue code example
<script setup>
import { ref } from 'vue'
const topic = "Variables Objects and Arrays"
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 Variables Objects and Arrays.
- 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 Variables Objects and Arrays and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Variables Objects and Arrays from Chapter 2. 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.
2.2 Functions and Arrow Functions
Functions and Arrow Functions is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 2, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Functions and Arrow Functions in Chapter 2, 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 Functions and Arrow Functions to javascript essentials for vue. 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
Functions and Arrow Functions is a focused part of Vue application design in Chapter 2. 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 profile editor that demonstrates Functions and Arrow Functions. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Functions and Arrow Functions is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 2, topic 2.
Example 2: Change one reactive value
Change one value involved in Functions and Arrow Functions inside the search panel. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use Functions and Arrow Functions across two components in the shopping cart. 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 lesson tracker. Handle the Functions and Arrow Functions edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Functions and Arrow Functions in the booking form while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Functions and Arrow Functions is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 2, topic 2.
Example 6: State ownership review
Remove duplicated state from the message panel. For Functions and Arrow Functions, derive values when possible and keep the writable source with the component or store that owns it.
Example 7: Slow-network scenario
Assume the admin table has a slow request while using Functions and Arrow Functions. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Functions and Arrow Functions responsibility from a crowded photo gallery into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the notification center before optimizing Functions and Arrow Functions. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Functions and Arrow Functions in the task board for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Functions and Arrow Functions is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 2, topic 2.
Vue code example
<script setup>
import { ref } from 'vue'
const topic = "Functions and Arrow Functions"
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 Functions and Arrow Functions.
- 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 Functions and Arrow Functions and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Functions and Arrow Functions from Chapter 2. 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.
2.3 Destructuring and Spread
Destructuring and Spread is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 2, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Destructuring and Spread in Chapter 2, 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 Destructuring and Spread to javascript essentials for vue. 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
Destructuring and Spread is a focused part of Vue application design in Chapter 2. 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 lesson tracker that demonstrates Destructuring and Spread. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Destructuring and Spread is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 2, topic 3.
Example 2: Change one reactive value
Change one value involved in Destructuring and Spread inside the booking form. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use Destructuring and Spread across two components in the message 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 admin table. Handle the Destructuring and Spread edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Destructuring and Spread in the photo gallery while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Destructuring and Spread is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 2, topic 3.
Example 6: State ownership review
Remove duplicated state from the notification center. For Destructuring and Spread, derive values when possible and keep the writable source with the component or store that owns it.
Example 7: Slow-network scenario
Assume the task board has a slow request while using Destructuring and Spread. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Destructuring and Spread responsibility from a crowded language selector into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the quiz screen before optimizing Destructuring and Spread. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Destructuring and Spread in the analytics view for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Destructuring and Spread is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 2, topic 3.
Vue code example
<script setup>
import { ref } from 'vue'
const topic = "Destructuring and Spread"
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 Destructuring and Spread.
- 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 Destructuring and Spread and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Destructuring and Spread from Chapter 2. 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.
2.4 Array Methods
Array Methods is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 2, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Array Methods in Chapter 2, 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 Array Methods to javascript essentials for vue. 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
Array Methods is a focused part of Vue application design in Chapter 2. 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 admin table that demonstrates Array Methods. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Array Methods is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 2, topic 4.
Example 2: Change one reactive value
Change one value involved in Array Methods inside the photo gallery. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use Array Methods across two components in the notification center. 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 task board. Handle the Array Methods edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Array Methods in the language selector while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Array Methods is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 2, topic 4.
Example 6: State ownership review
Remove duplicated state from the quiz screen. For Array Methods, derive values when possible and keep the writable source with the component or store that owns it.
Example 7: Slow-network scenario
Assume the analytics view has a slow request while using Array Methods. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Array Methods responsibility from a crowded support form into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the course dashboard before optimizing Array Methods. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Array Methods in the profile editor for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Array Methods is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 2, topic 4.
Vue code example
<script setup>
import { ref } from 'vue'
const topic = "Array Methods"
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 Array Methods.
- 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 Array Methods and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Array Methods from Chapter 2. 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.
2.5 Modules Promises and async await
Modules Promises and async await is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. In Chapter 2, trace the value or control flow from its source to the rendered interface so you can explain why Vue changes the screen.
For Modules Promises and async await in Chapter 2, 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 Modules Promises and async await to javascript essentials for vue. 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
Modules Promises and async await is a focused part of Vue application design in Chapter 2. 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 task board that demonstrates Modules Promises and async await. Keep one input and one visible result, then explain reactive inputs, component ownership, rendered output, edge cases, and what causes another update. Modules Promises and async await is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 1 for Chapter 2, topic 5.
Example 2: Change one reactive value
Change one value involved in Modules Promises and async await inside the language selector. Predict what Vue will update before running it, then compare the prediction with the rendered result.
Example 3: Parent-child comparison
Use Modules Promises and async await across two components in the quiz screen. 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 analytics view. Handle the Modules Promises and async await edge case explicitly instead of leaving stale output.
Example 5: Accessibility review
Use Modules Promises and async await in the support form while checking semantic HTML, labels, focus order, keyboard access, and understandable status feedback. Modules Promises and async await is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 5 for Chapter 2, topic 5.
Example 6: State ownership review
Remove duplicated state from the course dashboard. For Modules Promises and async await, derive values when possible and keep the writable source with the component or store that owns it.
Example 7: Slow-network scenario
Assume the profile editor has a slow request while using Modules Promises and async await. Decide what remains interactive, what shows pending feedback, and how stale responses are prevented.
Example 8: Refactoring exercise
Extract the Modules Promises and async await responsibility from a crowded search panel into a focused component or composable with a narrow API.
Example 9: Performance experiment
Measure the shopping cart before optimizing Modules Promises and async await. Check reactive work, repeated calculations, list size, component updates, and user-visible delay.
Example 10: Production review
Review Modules Promises and async await in the lesson tracker for errors, security, localization, RTL, narrow screens, accessibility, and what monitoring should report. Modules Promises and async await is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements. This is example 10 for Chapter 2, topic 5.
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 Modules Promises and async await.
- 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 Modules Promises and async await and updates according to the interaction or data in the example.
Practice exercise
Create a small Vue feature focused on Modules Promises and async await from Chapter 2. 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 2 review — 10 questions and answers
1. What is the purpose of Variables Objects and Arrays?
Answer: Variables Objects and Arrays is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
2. What should you inspect when Variables Objects and Arrays 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 Functions and Arrow Functions?
Answer: Functions and Arrow Functions is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
4. What should you inspect when Functions and Arrow Functions 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 Destructuring and Spread?
Answer: Destructuring and Spread is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
6. What should you inspect when Destructuring and Spread 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 Array Methods?
Answer: Array Methods is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
8. What should you inspect when Array Methods 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 Modules Promises and async await?
Answer: Modules Promises and async await is a focused part of Vue application design in Chapter 2. Study its inputs, reactive dependencies, component ownership, rendered result, edge cases, and cleanup requirements.
10. What should you inspect when Modules Promises and async await 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.