Question 1

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 2

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 3

When should you use readonly, markRaw, and toRaw in Vue reactivity?

Accepted Answer

**Target Audience:** Vue developers designing composables and stores, or integrating non-Vue libraries. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Warnings, outputs and timings below come from running code on Vue 3.5.44 (Node 22, and jsdom for the component); timings are from one sandbox machine. This page is the **decision guide**. The mechanics are covered by two sibling questions: [What does readonly do in Vue's rea

Question 4

How do dynamic components work?

Accepted Answer

**Target Audience:** Developers who know basic Vue templates and components and want to understand runtime component switching. **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 block in this doc was produced by compiling and running the code on Vue 3.5.44, either with the repo's verify-vue-example.mjs harness (compile t

Question 5

How do you render very large lists efficiently in Vue (virtual scrolling)?

Accepted Answer

**Target Audience:** Vue developers who have hit a slow page with a long list and want to explain or build virtual scrolling. Assumes v-for and computed. **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. The runnable list passed scripts/verify-vue-example.mjs on Vue 3.5.44 (mounted in jsdom, scrolled by settin

Question 6

What are shallowRef and shallowReactive?

Accepted Answer

**Target Audience:** Vue developers who know `ref` and `reactive` and want to understand the shallow variants exactly. **Difficulty:** Hard > **How to read this doc:** Plain language first, then 📌 Interview term: callouts with the vocabulary an interviewer listens for. Every console line and render count quoted below was produced by running the code on Vue 3.5.44, either as a Node script against the `vue` package or as an SFC mounted in jsdom with the repo verifier. This page expl

Question 7

When should you use shallowRef / shallowReactive / triggerRef?

Accepted Answer

**Target Audience:** Vue developers making performance or architecture decisions about reactive state. **Difficulty:** Hard > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Timings and outputs below come from running the code on Vue 3.5.44 (Node 22, and jsdom for the component). Timings are from one sandbox machine and will differ on yours; the ratios are the point. For the mechanics of the shallow APIs themselves (what is tracked, ref unwrapping,

Question 8

What are common reactivity caveats in Vue?

Accepted Answer

**Target Audience:** Developers who have shipped Vue 3 code and want to explain, not just recognise, the reactivity bugs that show up in code review. **Difficulty:** Hard > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Every symptom and every warning or error message below was produced on Vue 3.5.44: reactivity probes with node, the compiler check with @vue/compiler-sfc, and the components compiled and clicked in jsdom.

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Medium