Question 1

What is Vue.js and what are its core features?

Accepted Answer

**Target Audience:** Complete beginners preparing for a first Vue interview. Assumes you know a little HTML and JavaScript, nothing about Vue or any other framework. **Difficulty:** Easy > **How to read this doc:** Every idea is explained in plain language first, then tagged with 📌 Interview term: so you also learn the exact words an interviewer listens for. The outputs in sections 5 and 6 were produced by actually compiling and running the code on Vue 3.5.44, the current stable r

Question 2

What are Vue directives? Give common examples.

Accepted Answer

**Target Audience:** Beginners who can read a basic Vue template and want to understand every v- attribute they see. Basic HTML and JavaScript assumed. **Difficulty:** Easy > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The rendered output, the compiled render function and the warnings below come from compiling and mounting the example on Vue 3.5.44, not from memory. ## 1. Why This Even Matters — A Story First Imagine a theatre sc

Question 3

How do you render lists with v-for?

Accepted Answer

**Target Audience:** Beginners who need to show a list of things (products, messages, todos) in a Vue component. Basic JavaScript arrays and objects assumed. **Difficulty:** Easy > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Every rendered list, DOM-identity check and error message below came from mounting the code on Vue 3.5.44 in jsdom and clicking through it. ## 1. Why This Even Matters — A Story First Imagine you are writing place cards f

Question 4

What changed from Vue 2 to Vue 3, and what does Vue 2 end of life mean?

Accepted Answer

**Target Audience:** Developers who meet Vue 2 code at work, or see Vue 2 tutorials online, and need to explain what is different in Vue 3. Basic Vue knowledge helps but every term is defined. **Difficulty:** Easy > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The comparisons in sections 4 and 5 were not taken from the migration guide: the same code was run on **vue 2.7.16** and **vue 3.5.44** side by side in Node with jsdom, and the outputs are

Question 5

How do defineProps and defineEmits work in <script setup>?

Accepted Answer

**Target Audience:** Vue 3 developers using `<script setup>` who want to understand the two macros they write in almost every component.
**Difficulty:** Easy

> **How to read this doc:** Plain language first, then `📌 Interview term:` callouts. All compiled output and compiler errors come from `@vue/compiler-sfc` 3.5.44 `compileScript()`; runtime logs from a two-component app compiled the same way and mounted in jsdom; type errors from `vue-tsc` 3.3.13.

## 1. Why This Even Matters — A Story Fir

Question 6

What are scoped styles in Vue?

Accepted Answer

**Target Audience:** Vue developers who write `<style scoped>` and want to know precisely what it does and where its edges are.
**Difficulty:** Easy

> **How to read this doc:** Plain language first, then `📌 Interview term:` callouts. The compiled CSS is real output from `@vue/compiler-sfc` 3.5.44 `compileStyle()` and from a `vite build` (vite 8.3.4, `@vitejs/plugin-vue` 6.0.10). The DOM attributes come from mounting the components in jsdom, and the computed colours were read from the built app

Question 7

How does Vue's reactivity system work?

Accepted Answer

**Target Audience:** Anyone preparing for a Vue interview — assumes basic JavaScript objects and functions, no Vue internals required. **Difficulty:** Medium > **How to read this doc:** Each idea is explained in plain language first, then tagged with 📌 Interview term: so you also learn the words an interviewer listens for. Every output block below was produced by running the code on Vue 3.5.44: plain reactivity with node, components compiled with @vue/compiler-s

Question 8

What is the difference between watch and watchEffect?

Accepted Answer

**Target Audience:** Vue developers who reach for watchers and want to choose between the two on purpose rather than by habit. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts with the vocabulary interviewers listen for. Every output below was produced on Vue 3.5.44, with node for the reactivity probe and with @vue/compiler-sfc plus jsdom for the components. This page is about the *tracking model*; t

Question 9

What is the difference between ref and reactive?

Accepted Answer

**Target Audience:** Developers who have written a Vue 3 component or two and want to stop guessing between ref and reactive. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts with the vocabulary interviewers expect. Every output below was produced on Vue 3.5.44: the reactivity probe with node, the component by compiling it with @vue/compiler-sfc and clicking through it in js

Question 10

Why use storeToRefs with Pinia?

Accepted Answer

**Target Audience:** Anyone preparing for a Vue interview who has used [Pinia](/interview-question/what-is-pinia-and-why-use-it) at least once — basic ref and reactive knowledge assumed. **Difficulty:** Medium > **How to read this doc:** Ideas are explained in plain language first, then tagged with 📌 Interview term: so you also learn the words an interviewer listens for. Every output was produced on Vue 3.5.44 with pinia 4.1.0 (and 3.0.4 for one compariso

VUE.JSDECODED.

Easy

What is Vue.js and what are its core features?

What are Vue directives? Give common examples.

How do you render lists with v-for?

What changed from Vue 2 to Vue 3, and what does Vue 2 end of life mean?

How do defineProps and defineEmits work in <script setup>?

What are scoped styles in Vue?

Medium

How does Vue's reactivity system work?

What is the difference between watch and watchEffect?

What is the difference between ref and reactive?

Why use storeToRefs with Pinia?

What are provide and inject?

How do you handle forms and validation in Vue?

How do you use TypeScript with Vue (typed props, emits, refs, vue-tsc)?

What is Teleport in Vue 3?

Hard

What is Vapor mode in Vue 3.5+ and how does it differ from the virtual DOM?

What do markRaw and toRaw do?

What are shallowRef and shallowReactive?

When should you use shallowRef / shallowReactive / triggerRef?

What are common reactivity caveats in Vue?