Vue.js Interview Questions Quiz (2025 Edition) Quiz

Challenge your understanding of modern Vue.js concepts and features with this intermediate-level quiz designed for technical interviews in 2025. Assess your knowledge of state management, reactivity, lifecycle hooks, and advanced component usage in Vue.js.

1. Vue.js Reactivity System

   Which feature of Vue.js allows it to automatically track changes in data and update the UI efficiently, as seen when a value in the data property is changed?

   1. Context API
   2. Reactivity System
   3. Mutation Observer
   4. Router System

   Explanation: The Reactivity System in Vue.js ensures that changes in data are automatically reflected in the user interface. Router System is responsible for navigation and does not manage data changes. Context API is not a Vue.js term; it is associated with other frameworks. Mutation Observer is a low-level web API for DOM changes and not directly related to Vue's reactivity. Thus, the Reactivity System is the correct choice.

2. Vue Composition API Usage

   When using the Composition API in Vue.js, which function is employed to declare a reactive primitive, for example: const count = ___(0);?

   1. ref
   2. def
   3. react
   4. let

   Explanation: The ref function is used to create a reactive reference to a primitive value in the Composition API. The term 'def' does not exist in Vue.js, 'react' is a distractor that sounds similar but is incorrect, and 'let' is a standard JavaScript keyword, not part of Vue's API. Therefore, 'ref' is the accurate answer.

3. Component Communication Methods

   How can a child component in Vue.js send data to its parent component during an input event?

   1. By modifying a prop value directly
   2. By importing the parent instance
   3. By emitting an event using $emit
   4. By using v-model directly on the child

   Explanation: A child component communicates with its parent by emitting custom events through $emit, allowing the parent to listen and respond. Using v-model on the child does not directly transfer data upward; it's a syntactic sugar for props and events. Directly modifying prop values violates one-way data flow. Importing the parent instance is not a recommended or standard pattern in Vue.js. Hence, $emit is correct.

4. Lifecycle Hooks Understanding

   Which Vue.js lifecycle hook is called after the first rendering of the component, useful for tasks like fetching data from an API?

   1. created
   2. mounted
   3. computed
   4. beforeUnmount

   Explanation: The 'mounted' hook executes after the component is rendered in the DOM, making it ideal for tasks such as data fetching. 'beforeUnmount' is called just before a component is destroyed. 'created' is triggered after the component instance is created but before mounting. 'computed' is a property type, not a lifecycle hook. Therefore, 'mounted' is the right option.

5. State Management in Vue.js

   What is the primary benefit of using a centralized state management approach in a medium-sized Vue.js application with multiple interdependent components?

   1. It reduces application bundle size significantly
   2. It automatically handles routing between components
   3. It ensures consistency and easier debugging by managing shared state centrally
   4. It completely removes the need for props and events

   Explanation: Centralized state management helps maintain consistent data across components and simplifies debugging by storing shared state in one location. While it improves development workflow, it does not reduce bundle size by itself. Props and events may still be useful for some local communication. Centralized state has no role in routing, which is managed separately. Thus, the first option is correct.