Vue Interviews – Top Questions & Answers for Web Developers
Vue.js is a progressive JavaScript framework used to build user interfaces. It focuses on the view layer, allowing you to start small and scale into full applications using tools like Vue Router and Vuex/Pinia.
- Vue is easier to learn (HTML + JS + CSS).
- Lightweight runtime.
- Uses two-way binding like Angular and component-based UI like React.
- More flexible with API choices (Options API & Composition API).
The Virtual DOM is a lightweight JS representation of the real DOM. Vue updates only changed nodes, making rendering faster and more efficient.
Vue 3 introduced:
- Composition API
- Better performance
- Tree-shaking
- Fragments & Teleport
- Proxy-based reactivity (faster and more accurate)
A new way in Vue 3 to organize logic using setup() and reusable functions. It helps create cleaner, more scalable components.
The traditional Vue API using options like data(), methods, computed, and watch.
Use Composition API when:
- You have large components
- Complex logic needs to be organized
- Logic must be reused across components
A reusable UI block defined using HTML, CSS, and JavaScript.
Files with .vue extension containing:
<template><script><style>
They keep component logic clean and modular.
It binds dynamic data to attributes. Example:
<img v-bind:src="imageUrl" />The colon :
<img :src="imageUrl" />Creates two-way data binding, commonly used with inputs.
Options API:
- beforeCreate
- created
- beforeMount
- mounted
- beforeUpdate
- updated
- beforeUnmount
- unmounted
Composition API:
- onMounted
- onUpdated
- onUnmounted
- onBeforeMount
- onBeforeUpdate … and more.
A cached value based on reactive data.
A watcher runs code when a specific data property changes. Useful for API calls or expensive operations.
Vue’s official routing library for building single-page applications.
Routes with parameters:
/users/:id
Functions that check access before entering a route—useful for authentication.
A state management library for Vue 2 & Vue 3 following the Flux pattern.
Pinia is the new recommended state management library for Vue 3—lighter, simpler, and more modular than Vuex.
To offer:
- TypeScript support
- Modular stores
- Better DevTools
- Simpler usage
Using ref() or reactive() for reactivity.
Example:
const count = ref(0);ref→ single valuereactive→ objects/arrays
HTML containing interpolations and directives to render dynamic content.
Special HTML markers starting with v- like:
v-ifv-forv-model
Conditionally renders or removes elements from the DOM.
v-ifremoves/adds elements.v-showtoggles CSSdisplay.
To loop through arrays or objects.
It helps Vue track DOM elements efficiently.
Slot is a content placeholder allowing components to accept external HTML.
Slots with custom names:
<slot name="header"></slot>Slots that receive data from the child component.
A feature to render part of a component in another part of the DOM (e.g., modal root).
Components that return multiple root elements.
Entry point for Composition API logic.
Reusable logic functions like:
useFetch()
useAuth()
Vue 2 could not detect:
- new object keys
- array index changes Vue 3 fixed this using proxies.
Using fetch, axios, or inside hooks like onMounted().
A synchronous way to modify state.
Handles async logic before committing mutations.
Computed values for the store.
A modular state container created using defineStore.
Pinia is:
- Simpler
- No mutations
- Fully TS ready
- DevTools friendly
- use computed
- memoize heavy values
- lazy-loading routes
- avoid unnecessary watchers
- use
v-oncefor static content
Used to attach event listeners.
Shorthand: @
A way to access DOM elements directly.
Old reuse pattern before Composition API. Avoid in Vue 3—use composables instead.
Globally adds functionality like UI libraries or custom services.
Vue 3 removes unused code during build for smaller bundles.
Matching client JS to server-rendered HTML.
A framework built on Vue for SSR, routing, and full-stack applications.
Automatically tracks reactive dependencies inside watchEffect().
Runs logic whenever its dependencies change—no need to specify values.
Used inside <script setup> to declare props.
Defines custom events for parent-child communication.
Reactive reference but tracks only the top-level value.
Allows async components with fallback loading UI.
Converts a reactive object’s properties into individual refs.
Way to share data deeply across component trees.
- Props → passed from parent
- State → owned by component/store
A component registered once and used anywhere.
Registered inside another component.
emit("submit", data)$emit triggers events; callbacks pass functions as props.
For static content that never changes.
Prevents flash of uncompiled template.
Load components or routes only when needed.
Breaking the bundle into smaller chunks for faster loading.
Dynamic component rendering.
Caches component state when switching between views.
For adding animations to elements entering or leaving the DOM.
For list animations.
Executes code after DOM updates.
Vue without template compiler—used with precompiled templates.
Includes template compiler for in-browser template building.
Watching nested objects using:
deep: trueA value that triggers updates when changed.
Helps Vue efficiently update DOM elements in lists.
A component pattern that returns another component.
It violates one-way data flow.
Use computed setter or local data copies.
async setup() lets you await API calls before rendering.
A component loaded with dynamic import.
Render only visible DOM elements for huge lists.
Using Vue DevTools extension.
A JavaScript function that returns VNodes instead of templates.
When dynamic template generation is required.
An alternative to templates using JavaScript XML syntax.
Similar to reactive() but only tracks the top-level properties.
A component whose input value is bound using v-model.
To define event names and validate payloads.
Using composables.
- Props → data passing
- Slots → template passing
Vue packaged in ES module format.
Adds global variables or functions to Vue application.
A return function inside watch() to stop listening.
Used to reference DOM elements in Composition API via ref().
For SEO, faster first paint, and content-heavy apps.
When client-side DOM doesn’t match server-rendered DOM.
Vue offers:
- Flexibility
- Clean architecture
- Fast performance
- Easy learning curve
- Strong ecosystem
- Long-term stability (Vue 3 foundation)