Question 1

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 2

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 3

What is the difference between computed and watch?

Accepted Answer

**Target Audience:** Vue developers who use both APIs and want a crisp rule for choosing, plus the reasons behind it. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts with the precise vocabulary. Every output below was produced on Vue 3.5.44: the probes with node, the component by compiling it with @vue/compiler-sfc and typing into it in jsdom. ## 1. Why This Even Matters — A Story First A café has

Question 4

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

Question 5

watch vs watchEffect — flush timing and the new watch options in 3.5?

Accepted Answer

**Target Audience:** Developers who already know [watch vs watchEffect](/interview-question/what-is-the-difference-between-watch-and-watcheffect) and want the precise timing model plus the 3.4 and 3.5 additions. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. This page is entirely about ordering and timing, so every ordering claim below comes from a console.log-instrumented run on Vue 3.5.44 (components compile

Question 6

What is nextTick in Vue?

Accepted Answer

**Target Audience:** Vue developers who have been bitten by "the DOM has not updated yet" and want the exact timing, not just "use nextTick". **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. This topic is all about ordering, so every ordering claim below comes from a console.log-instrumented run on Vue 3.5.44: components compiled with @vue/compiler-sfc and clicked in jsdom, plus a Vitest and Vue Tes

VUE.JSDECODED.

Easy