Vue.js Interview Questions and Answers

Vue.js interview questions — the reactivity system, components and props, computed vs methods vs watchers, lifecycle hooks, and Options vs Composition API.

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Vue.js

19Questions

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Basic to AdvancedDifficulty

Fresher to 5+ YrsExperience

All Vue.js Questions (19) Sort by

01 What is the difference between v-if and v-show in Vue? v-if adds or removes the element (and its component, listeners, child components) from the DOM entirely — higher… Templates Basic Fresher
02 Why do you need a key when rendering a list (v-for / ng-repeat / React)? The key gives each list item a stable identity so the framework's diffing algorithm can match old and new items and… Templates Intermediate 1–2 Yrs
03 How do parent and child components communicate in Vue? Data flows down via props and events flow up via emit. A parent passes data to a child as props (read-only in the… Components Basic 1–2 Yrs
04 What are the Vue component lifecycle hooks? The main hooks are beforeCreate/created (state ready, no DOM), beforeMount/mounted (DOM available),… Components Intermediate 2–3 Yrs
05 What is the difference between the Options API and the Composition API in Vue? The Options API organises a component by option type — data, methods, computed, watch. The Composition API (Vue 3)… Components Intermediate 2–3 Yrs
06 What is the difference between ref and reactive in Vue 3? ref(value) wraps any value (primitive or object) in a reactive box you access via .value. reactive(obj) makes an… Reactivity Intermediate 2–3 Yrs
07 When should you use a watcher in Vue instead of a computed property? Use a computed to derive a value you display. Use a watcher when a change should trigger a side effect — call an API,… Reactivity Intermediate 1–2 Yrs
08 What are slots in Vue? Slots let a parent pass template content into a child component — content projection. A default slot is the child's… Components Intermediate 2–3 Yrs
09 What is Pinia (or Vuex), and when do you need a state store? Pinia (the current standard; Vuex was the predecessor) is a centralized store for state that many unrelated components… State Management Intermediate 2–3 Yrs
10 What are the main differences between Vue 2 and Vue 3? Vue 3 rebuilt reactivity on ES6 Proxy (Vue 2 used Object.defineProperty, which couldn't detect added properties or… Fundamentals Basic 1–2 Yrs
11 How does routing work in a Vue single-page app? Vue Router maps URL paths to components rendered in <router-view>, without a full page reload. It supports dynamic… Routing Intermediate 2–3 Yrs
12 What does putting :key on a component (not in v-for) do? Changing a component's :key tells Vue to destroy the old instance and create a fresh one, resetting all its internal… Templates Intermediate 2–3 Yrs
13 What is provide/inject in Vue, and when do you use it? provide lets an ancestor component expose a value that any descendant can inject, no matter how deep — avoiding “prop… Components Intermediate 2–3 Yrs
14 What is the virtual DOM, and does it always make things faster? The virtual DOM is a lightweight JS representation of the UI. On a state change, the framework builds a new vDOM tree,… Reactivity Advanced 3–5 Yrs
15 How does v-model work on a custom component? v-model on a component is sugar for a modelValue prop plus an update:modelValue event. The child renders the prop and… Components Intermediate 2–3 Yrs
16 What is nextTick in Vue? Vue batches DOM updates — when you change reactive state, the DOM isn't updated synchronously. await nextTick() (or… Reactivity Advanced 3–5 Yrs
17 What is a composable in Vue, and how does it replace mixins? A composable is a plain function (by convention useSomething()) that uses Composition API primitives (ref, computed,… Components Intermediate 2–3 Yrs
18 How does Vue's reactivity system work? Vue tracks which parts of your component's render depend on which reactive properties. When a component renders, Vue… Reactivity Intermediate 2–3 Yrs
19 What is the difference between computed properties, methods and watchers in Vue? A computed property is a cached derived value — it only recalculates when one of its reactive dependencies changes,… Reactivity Basic 1–2 Yrs

About these Vue.js questions

Vue is a common choice for new frontends on .NET APIs. Interviewers ask about the reactivity system (how Vue tracks dependencies and re-renders), the difference between computed, methods and watch, one-way props with events up, lifecycle hooks, and when to reach for the Composition API.

Vue.js Interview Questions and Answers

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About these Vue.js questions