Q: What is a Single File Component (SFC)?

**Target Audience:** Beginners who have seen .vue files but do not know what is inside one or what happens to it. Basic HTML, CSS and JavaScript assumed. **Difficulty:** Easy > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The compiled JavaScript and CSS in sections 5 and 6 are the real, unedited output of @vue/compiler-sfc 3.5.44, the same compiler @vitejs/plugin-vue calls during a Vite build. The runnable

Question 1

What are dynamic arguments and v-bind shorthand?

Accepted Answer

**Target Audience:** Vue beginners who know what `v-bind` and `v-on` do and want the full picture of their syntax.
**Difficulty:** Easy

> **How to read this doc:** Plain language first, then `📌 Interview term:` callouts. The compiled code, compiler errors, runtime errors and DOM output below came from running Vue 3.5.44 (`@vue/compiler-dom` for compiler output, jsdom for the runtime).

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

Think of a label maker at a warehouse. Normally the operator typ

Question 2

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 3

What is a Single File Component (SFC)?

Accepted Answer

**Target Audience:** Beginners who have seen .vue files but do not know what is inside one or what happens to it. Basic HTML, CSS and JavaScript assumed. **Difficulty:** Easy > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The compiled JavaScript and CSS in sections 5 and 6 are the real, unedited output of @vue/compiler-sfc 3.5.44, the same compiler @vitejs/plugin-vue calls during a Vite build. The runnable

Question 4

What is Nuxt and how does it relate to Vue?

Accepted Answer

**Target Audience:** Vue developers who have heard of Nuxt and need to explain what it adds. No Nuxt experience 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. Everything in the "Verified" sections comes from a real Nuxt 4.6.1 project created for this answer: built with nuxt build, run as a production server, fetched with

Question 5

What is keep-alive in Vue?

Accepted Answer

**Target Audience:** Developers who know components and [dynamic components](/interview-question/how-do-dynamic-components-work) and want to keep state across switches. **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 hook log and warning below was produced by compiling and mounting the code on Vue 3.5.44 in jsdom with the repo's ver

Question 6

Why was Reactivity Transform ($ref, $computed) removed in Vue 3.4?

Accepted Answer

**Target Audience:** Vue developers maintaining or interviewing about code from the 3.2/3.3 era, and anyone curious why Vue still makes you type .value. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Dates and the deprecation history come from the vuejs/core changelogs, the Vue blog and the original RFC discussion, linked inline. What happens to old code today was checked by compiling and running it on Vue 3.5

Question 7

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

Accepted Answer

**Target Audience:** Vue developers who know templates and reactivity and want to understand Vapor mode precisely, including its release status. No compiler background needed. **Difficulty:** Hard > **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. Vapor output in this doc was produced with **vue 3.6.0-rc.12**, a release candidate: compiled with its @vue/compiler-s

Question 8

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

Accepted Answer

**Target Audience:** Vue and TypeScript developers who build reusable components such as lists, tables and selects.
**Difficulty:** Hard

> **How to read this doc:** Plain language first, then `📌 Interview term:` callouts. All type errors below are real output from `vue-tsc` 3.3.13 (TypeScript 5.9, `strict: true`) run on the example files; the compiled output comes from `@vue/compiler-sfc` 3.5.44; the runnable example was mounted in jsdom on Vue 3.5.44.

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

Question 9

When should you choose Vapor over VDOM in a real app — trade-offs?

Accepted Answer

**Target Audience:** Senior Vue developers and tech leads deciding whether and where to adopt Vapor mode. Assumes you know what Vapor is; if not, read [What is Vapor mode](/interview-question/what-is-vapor-mode-in-vue-3-5-and-how-does-it-differ-from-the-virtual-dom) first. **Difficulty:** Hard > **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. All numbers here were meas

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