Question 1

What are props in Vue and how do you validate them?

Accepted Answer

**Target Audience:** Vue beginners who have built a component or two and now need them to accept configuration from a parent.
**Difficulty:** Easy

> **How to read this doc:** Plain language first, then `📌 Interview term:` callouts. Every warning message, rendered value and production-build result quoted below came from running the code on Vue 3.5.44, compiled with `@vue/compiler-sfc` and mounted in jsdom, in development and production mode.

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

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Question 2

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 3

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 4

How do you create a new Vue 3 app, and what is in the project structure?

Accepted Answer

**Target Audience:** Beginners who have never set up a frontend project. Assumes Node.js is installed and you can type commands in a terminal; no Vue, Vite or build-tool knowledge needed. **Difficulty:** Easy > **How to read this doc:** Plain language first, then 📌 Interview term: callouts with the vocabulary an interviewer expects. Nothing below is from memory: the project was generated by running create-vue 3.24.0 non-interactively in a sandbox, then installed, type-checked, bui

Question 5

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 6

How do you make provide/inject type-safe?

Accepted Answer

**Target Audience:** Vue developers using TypeScript. Assumes you know what [provide and inject](/interview-question/what-are-provide-and-inject) do; this doc is only about typing them. **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. The type errors quoted here are the real output of vue-tsc 3.3.13 on Vue 3.5.44, and the runtime ou

Question 7

Why declare emits and can you validate them?

Accepted Answer

**Target Audience:** Vue developers who emit events from components and want to know what declaring them actually changes.
**Difficulty:** Medium

> **How to read this doc:** Plain language first, then `📌 Interview term:` callouts. Every log line and warning below came from running the code on Vue 3.5.44, compiled with `@vue/compiler-sfc` and mounted in jsdom, in development and in production mode.

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

A restaurant kitchen has a list of bells on the wal

Question 8

What is defineModel() in Vue 3.4+ and how does it replace manual prop + emit?

Accepted Answer

**Target Audience:** Vue 3 developers who know the [component v-model contract](/interview-question/how-does-v-model-work-on-components) and want to know what `defineModel()` really does.
**Difficulty:** Medium

> **How to read this doc:** Plain language first, then `📌 Interview term:` callouts. The compiled output is from `@vue/compiler-sfc` 3.5.44 `compileScript()`, and every value read after a click or keystroke came from mounting the components in jsdom on Vue 3.5.44. Version history comes

Question 9

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

Accepted Answer

**Target Audience:** Vue developers adopting TypeScript, or TypeScript developers new to Vue's single file components.
**Difficulty:** Medium

> **How to read this doc:** Plain language first, then `📌 Interview term:` callouts. Every type error below is real output from `vue-tsc` 3.3.13 with TypeScript 5.9 and `strict: true`; compiled output comes from `@vue/compiler-sfc` 3.5.44; runtime behaviour and warnings come from mounting the components in jsdom on Vue 3.5.44; the `vite build` result is

Question 10

What is defineExpose?

Accepted Answer

**Target Audience:** Anyone preparing for a Vue interview who has used `

VUE.JSDECODED.

Easy

What are props in Vue and how do you validate them?

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>?

How do you create a new Vue 3 app, and what is in the project structure?

Medium

What is the difference between ref and reactive?

How do you make provide/inject type-safe?

Why declare emits and can you validate them?

What is defineModel() in Vue 3.4+ and how does it replace manual prop + emit?

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

What is defineExpose?

How do you add global properties or config?

What are slots in Vue?

Hard

How do generic <script setup> components work (generic="T")?