Question 1

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 2

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 3

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

Question 4

How do you access a DOM element or child component instance?

Accepted Answer

**Target Audience:** Anyone preparing for a Vue interview. Assumes you know `ref()` and lifecycle hooks at a basic level. **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. All output in the "Verified" sections was produced on Vue 3.5.44 with the repo verifier (compiled and mounted in jsdom) and with Vitest and Vue Test Utils. Real browser layout

Question 5

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 6

What is defineExpose?

Accepted Answer

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

Question 7

What is useTemplateRef() (Vue 3.5) and how does it improve on ref=""?

Accepted Answer

**Target Audience:** Vue developers who already use template refs and want to know what changed in 3.5. The general rules for refs (timing, `v-for`, component instances) are in [accessing a DOM element or child component instance](/interview-question/how-do-you-access-a-dom-element-or-child-component-instance). **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 interviewe

Question 8

What is defineExpose() and why are <script setup> components closed by default?

Accepted Answer

**Target Audience:** Vue developers who know template refs and are moving from the Options API to `

Question 9

How do Vue components communicate?

Accepted Answer

**Target Audience:** Anyone preparing for a Vue interview. Assumes basic JavaScript; no prior Vue knowledge needed. **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 quoted in the "Verified" sections was produced by running the code on Vue 3.5.44, either with the repo verifier (compiled with @vue/compiler-sfc and mounted

Question 10

How do you test Vue components (Vitest and Vue Test Utils)?

Accepted Answer

**Target Audience:** Anyone preparing for a Vue interview who can write [Single File Components](/interview-question/what-is-a-single-file-component-sfc) — no testing experience required. **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 test in this doc was actually run: Vitest 5.0.5 with @vitejs/plugin-vue 6.0.10, @vue/test-utils 2.5.1, j

VUE.JSDECODED.

Medium

What is the difference between watch and watchEffect?

What is the difference between ref and reactive?

Why use storeToRefs with Pinia?

How do you access a DOM element or child component instance?

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

What is defineExpose?

What is useTemplateRef() (Vue 3.5) and how does it improve on ref=""?

What is defineExpose() and why are <script setup> components closed by default?

Hard

How would you structure state management for a large Vue app?

What are shallowRef and shallowReactive?

What are common reactivity caveats in Vue?