Question 1

What is Vue.js?

Accepted Answer

Vue.js is a progressive JavaScript framework for building user interfaces. It features a reactive data binding system, component-based architecture, and virtual DOM for efficient rendering. Vue is incrementally adoptable—use it for a single widget or full single-page application. It's known for gentle learning curve, excellent documentation, and flexibility between Options API and Composition API.

Question 2

What are Vue directives?

Accepted Answer

Directives are special attributes prefixed with 'v-' that apply reactive behavior to the DOM. Common directives: v-bind (: shorthand) binds attributes to expressions, v-on (@ shorthand) attaches event listeners, v-model creates two-way binding on form inputs, v-if/v-else/v-show for conditional rendering, v-for for list rendering. Custom directives can be created for DOM manipulation.

Question 3

What is the difference between v-if and v-show?

Accepted Answer

v-if conditionally renders elements—false means the element isn't in the DOM at all. v-show always renders the element but toggles CSS display property. Use v-if for conditions that rarely change (lower initial render cost if false) and v-show for frequent toggling (no re-render cost). v-if supports v-else and v-else-if; v-show doesn't work with template element.

Question 4

What are computed properties and how do they differ from methods?

Accepted Answer

Computed properties are cached reactive values that recalculate only when dependencies change. Methods execute every time they're called. Use computed for derived data (filtering lists, formatting), methods for actions or when caching isn't needed. Computed properties are accessed like properties (no parentheses), can have getters and setters, and improve performance through caching.

Question 5

What are Vue lifecycle hooks?

Accepted Answer

Lifecycle hooks are methods called at specific stages of a component's existence. Creation: beforeCreate, created (data reactive, no DOM). Mounting: beforeMount, mounted (DOM available). Updating: beforeUpdate, updated (after re-render). Destruction: beforeUnmount, unmounted. Use mounted for DOM operations, created for data fetching, unmounted for cleanup. Composition API uses onMounted, onUnmounted, etc.

Question 6

How do parent and child components communicate?

Accepted Answer

Props down, events up. Parents pass data to children via props (one-way binding). Children emit custom events to parents using $emit('event-name', data). Parent listens with @event-name. For complex state, use Vuex/Pinia or provide/inject for dependency injection. Avoid mutating props directly—emit events to request changes from the parent.

Question 7

What are slots in Vue?

Accepted Answer

Slots allow parent components to inject content into child component templates. Default slot: receives content between component tags. Named slots: with

Question 8

What is Vuex and when should you use it?

Accepted Answer

Vuex is Vue's official state management library implementing Flux pattern. Core concepts: state (single source of truth), getters (computed state), mutations (synchronous state changes), actions (async operations that commit mutations). Use Vuex for shared state across many components, complex data flows, or when prop drilling becomes unwieldy. For Vue 3, Pinia is the recommended alternative.

Question 9

What is Vue Router?

Accepted Answer

Vue Router is the official routing library for Vue single-page applications. It maps URL paths to components, supports dynamic routes (/user/:id), nested routes, navigation guards (beforeEach, beforeEnter for access control), and lazy loading via dynamic imports. Features include programmatic navigation (router.push), route params/query, and HTML5 history or hash mode.

Question 10

What are navigation guards in Vue Router?

Accepted Answer

Navigation guards control route access and navigation flow. Global guards: beforeEach (authentication), afterEach (analytics). Per-route: beforeEnter in route config. In-component: beforeRouteEnter, beforeRouteUpdate, beforeRouteLeave. Guards receive to, from, and next parameters. Call next() to proceed, next(false) to cancel, or next('/path') to redirect. Essential for protected routes.

Question 11

What is the Composition API?

Accepted Answer

The Composition API (Vue 3) organizes code by logical concern rather than options (data, methods, computed). Use setup() function or <script setup> syntax. Features: ref() and reactive() for reactivity, computed() for derived values, watch/watchEffect for side effects. Benefits: better TypeScript support, code reuse via composables (custom hooks), improved organization for complex components.

Question 12

What are composables in Vue?

Accepted Answer

Composables are reusable functions using Composition API that encapsulate and share stateful logic across components. Convention: name with 'use' prefix (useFetch, useAuth). They return reactive state and methods. Example: useMouse() returns reactive x, y coordinates. Composables replace mixins with better TypeScript support, explicit dependencies, and no naming conflicts. Import and call in setup().

Question 13

What are Single File Components (SFCs)?

Accepted Answer

SFCs (.vue files) encapsulate template, script, and style in one file.

Question 14

How does Vue's reactivity system work?

Accepted Answer

Vue 3 uses JavaScript Proxies to track property access and modifications. When reactive data is read during render, it's tracked as a dependency. When data changes, Vue triggers re-renders for dependent components. Reactivity works with objects and arrays automatically. Pitfalls: adding new properties to plain objects (use reactive()), replacing entire reactive objects loses reactivity. ref() wraps primitives.

Question 15

How do you optimize Vue application performance?

Accepted Answer

Key optimizations: use v-show for frequent toggles, v-once for static content, lazy load routes and components with defineAsyncComponent. Use computed properties over methods for caching. Implement virtual scrolling for long lists. Use key attribute properly in v-for. Avoid unnecessary watchers. Use shallowRef/shallowReactive for large objects. Profile with Vue DevTools and optimize identified bottlenecks.

Basic Concepts(7 questions)

What is Vue.js and what are its primary purposes?

How can you include Vue in a project? What are some different ways to set it up?

What is a Vue instance and what are the key options you can define on it?

How do data binding and interpolation work in Vue?

What is the role of directives in Vue, and can you give examples of common directives?

How do you handle events in Vue templates?

What are filters in Vue and how are they used?

Component Fundamentals(7 questions)

How do you define a component in Vue, and what is the significance of passing props?

What is the difference between local and global registration of components?

What lifecycle hooks are available in Vue components and why are they useful?

How can you communicate between parent and child components?

What are custom events and how are they used in Vue for communication?

How can slots be used to create flexible components?

What are scoped slots and how do they differ from regular slots?

Intermediate Topics(8 questions)

What are computed properties and how do they differ from methods in Vue?

How does Vue handle watchers and when should you use them?

What is mixin and how does it help in code reuse?

How does Vue's reactivity system work, and what are some potential pitfalls with reactivity?

Can you explain the concept of "virtual DOM" in Vue and its benefits?

What is the Vue CLI and how does it support modern development workflows?

How would you optimize a Vue application for performance?

What are single file components (SFCs) and what advantages do they provide?

State Management(5 questions)

What is Vuex and why would you use it in a project?

Can you explain the key concepts of state, getters, mutations, and actions in Vuex?

How do you structure and manage large amounts of application state using Vuex?

What are some common patterns or best practices for using Vuex with Vue components?

How would you debug state issues in a Vue/Vuex application?

Routing and Navigation(5 questions)

What is Vue Router and why is it important in single-page applications?

How do you define routes in a Vue application and what are dynamic routes?

What are navigation guards and how do they help in controlling access to routes?

How can you handle nested or child routes with Vue Router?

What strategies can you use to lazy load routes for a Vue app?

Composition API and Advanced Patterns(6 questions)

What is the Composition API and how does it differ from the Options API?

How do you declare reactive variables and computed properties using the Composition API?

What are lifecycle hooks in the context of the Composition API and how are they utilized?

Can you explain how to reuse code across components with Composition API's custom hooks (composables)?

What are some challenges you might encounter when migrating from the Options API to the Composition API?

How do you handle code organization and modularization for large-scale Vue applications?

Testing and Best Practices(5 questions)

What are some common strategies for testing Vue components?

How do you use tools like Vue Test Utils to facilitate unit testing?

What is end-to-end (E2E) testing and which tools would you consider for a Vue application?

What best practices do you follow when structuring and writing Vue applications?

How do you ensure accessibility and performance in Vue applications?

Miscellaneous Advanced Topics(5 questions)

How does server-side rendering (SSR) work with Vue and what benefits does it offer?

What are some considerations for deploying a Vue application to production?

How do you handle asynchronous data fetching in Vue and what patterns help make it efficient?

Can you explain how to integrate Vue with other libraries or frameworks in a project?

What are some security concerns you need to be aware of when developing a Vue application?