Question 1

How do you add global properties or config?

Accepted Answer

**Target Audience:** Vue developers setting up an app's entry file, or migrating `Vue.prototype` code from Vue 2.
**Difficulty:** Medium

> **How to read this doc:** Plain language first, then `📌 Interview term:` callouts. The runtime output below came from bundling the example (`main.js` plus three SFCs) with esbuild and running it in jsdom on Vue 3.5.44; the TypeScript errors came from `vue-tsc` 3.3.13 with `strict: true`.

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

Think of an office build

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

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 4

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 5

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 6

How does the Vue compiler optimize templates (static hoisting, patch flags, block tree)?

Accepted Answer

**Target Audience:** Vue developers who know the virtual DOM exists and want to explain how Vue makes it cheap. 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. Every compiled snippet is real output of @vue/compiler-sfc 3.5.44 compileTemplate() (production mode), with one comparison against

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 is lazy hydration in Vue 3.5 — hydrate strategies (idle, visible, interaction)?

Accepted Answer

**Target Audience:** Developers with a server-rendered Vue or Nuxt app who want to cut the time before the page responds. Assumes you know what hydration is. **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 timelines in sections 5 and 6 were recorded in headless Chromium (Playwright) against a page server-rendered with Vue 3.5.44. The edge cas

VUE.JSDECODED.

Medium