Q: What do toRef and toRefs do?

**Target Audience:** Vue developers who know ref and reactive and keep seeing toRefs in composables without being sure what it buys them. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Every output below was produced on Vue 3.5.44: the probe with node , the component compiled with @vue/compiler-sfc and clicked in jsdom. The source excerpt is copied from the in

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 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 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 4

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 5

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 6

What are provide and inject?

Accepted Answer

**Target Audience:** Anyone preparing for a Vue interview. Assumes you know props and `ref()`. **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 in the "Verified" sections was produced on Vue 3.5.44: the runnable example with the repo verifier (compiled and mounted in jsdom), the app-level behaviour with a Node script against the sam

Question 7

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 8

How do you optimize performance in a Vue app?

Accepted Answer

**Target Audience:** Vue developers who have shipped an app and now need a method for making it faster. Assumes the Composition API basics. **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 number here was measured for this answer on Vue 3.5.44: the re-render counts by mounting the runnable example in jsdom with scripts/verify-vue-exa

Question 9

What does readonly do in Vue's reactivity?

Accepted Answer

**Target Audience:** Vue developers who share state between components, stores or composables. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Every warning message and value below was printed by running the code on Vue 3.5.44, both as Node scripts against the vue package and as an SFC mounted in jsdom. This page explains **what** readonly does. For **when** to use it next to markRaw a

Question 10

What do toRef and toRefs do?

Accepted Answer

**Target Audience:** Vue developers who know ref and reactive and keep seeing toRefs in composables without being sure what it buys them. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Every output below was produced on Vue 3.5.44: the probe with node, the component compiled with @vue/compiler-sfc and clicked in jsdom. The source excerpt is copied from the in

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Easy

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

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

Medium

How does Vue's reactivity system work?

What is the difference between ref and reactive?

Why use storeToRefs with Pinia?

What are provide and inject?

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

How do you optimize performance in a Vue app?

What does readonly do in Vue's reactivity?

What do toRef and toRefs do?

Hard

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

When should you use shallowRef / shallowReactive / triggerRef?

What are common reactivity caveats in Vue?

What is a custom renderer in Vue (createRenderer)?

How does server-side rendering work in Vue (renderToString, hydration)?