Latest Top interview questions and answers for a VUE JS developer for experienced and freshers, get ready to crack any interview.

Basics of Vue.js interview question:

1. What is Vue.js?
   • Answer: Vue.js is a progressive JavaScript framework for building user interfaces. It is designed from the ground up to be incrementally adaptable and focuses on the view layer of an application.
2. Explain the key features of Vue.js.
   • Answer: Vue.js includes features such as declarative rendering, two-way data binding, directives, components, and a virtual DOM. It is lightweight and easy to integrate into existing projects.
3. What is the Vue instance?
   • Answer: The Vue instance is the root of a Vue application. It is created by instantiating the Vue constructor and serves as the entry point for building Vue applications.
4. Explain data binding in Vue.js.
   • Answer: Data binding in Vue.js is the automatic synchronization of the view and the model. Changes in the model (data) are reflected in the view, and vice versa.
5. What is the purpose of the Vue template?
   • Answer: The Vue template is the HTML markup where Vue.js expressions and directives can be used to define the structure of the rendered view.
6. Explain the concept of directives in Vue.js.
   • Answer: Directives in Vue.js are special tokens in the markup that tell the library to do something to a DOM element. Examples include v-bind, v-model, and v-for.
7. What is the Vue component?
   • Answer: A Vue component is a reusable and self-contained unit that encapsulates a specific piece of functionality. Components can have their own state, methods, and lifecycle hooks.
8. How does Vue.js support component communication?
   • Answer: Vue.js supports component communication through props for parent-to-child communication, custom events for child-to-parent communication, and a centralized event bus for sibling components.
9. What is the Vue virtual DOM, and why is it important?
   • Answer: The Vue virtual DOM is a lightweight copy of the actual DOM. It allows Vue.js to perform efficient updates by comparing the virtual DOM with the actual DOM and updating only the changed parts.
10. Explain the concept of computed properties in Vue.js.
    • Answer: Computed properties in Vue.js are properties whose values are derived from other reactive data. They are cached based on their dependencies and are recalculated only when those dependencies change.

Advanced Vue.js Concepts interview question:

11. What are mixins in Vue.js, and how are they used?
    • Answer: Mixins are a way to distribute reusable functionalities across Vue components. They can contain data, methods, computed properties, and lifecycle hooks that can be merged into a component.
12. What is the Vuex state management pattern?
    • Answer: Vuex is the state management pattern for Vue.js applications. It includes a centralized store that holds the application state and serves as a single source of truth.
13. Explain the concept of watchers in Vue.js.
    • Answer: Watchers in Vue.js allow you to perform asynchronous or expensive operations in response to changes in data. They are defined in the watch option of a component.
14. What is the purpose of Vue.js transitions and animations?
    • Answer: Vue.js transitions and animations allow you to apply CSS transitions and animations to elements when they are inserted, updated, or removed from the DOM.
15. How does Vue.js handle routing in single-page applications (SPA)?
    • Answer: Vue Router is used to handle routing in Vue.js single-page applications. It allows you to define routes and associate them with components.
16. What is the purpose of the Vue.js v-for directive?
    • Answer: The v-for directive in Vue.js is used for rendering a list of items. It iterates over an array or object and creates a template for each item.
17. Explain the concept of dynamic components in Vue.js.
    • Answer: Dynamic components in Vue.js allow you to switch between multiple components at runtime. They are created using the component element and can be dynamically bound to a component.
18. How can you handle forms and form validation in Vue.js?
    • Answer: Vue.js provides the v-model directive for two-way data binding with form inputs. Form validation can be done using built-in directives and custom validation methods.
19. What is server-side rendering (SSR) in Vue.js?
    • Answer: Server-side rendering in Vue.js involves rendering Vue components on the server before sending the HTML to the client. It improves performance and search engine optimization (SEO).
20. Explain the concept of scoped slots in Vue.js.
    • Answer: Scoped slots in Vue.js allow a child component to pass data to a parent component. They enable more flexible and dynamic content distribution between components.

Testing in Vue.js interview question:

21. How can you perform unit testing in Vue.js?
    • Answer: Unit testing in Vue.js can be performed using testing frameworks like Jest or Mocha. Vue Test Utils provides utilities for testing Vue components.
22. What is the purpose of the shallowMount function in Vue.js testing?
    • Answer: The shallowMount function in Vue.js testing is used to mount a component for testing without rendering its child components. It provides a shallow rendering of the component.
23. How can you mock API calls in Vue.js testing?
    • Answer: API calls in Vue.js testing can be mocked using tools like axios-mock-adapter or by creating manual mocks. This allows isolated testing of components without making actual network requests.
24. What is end-to-end testing in Vue.js, and how is it done?
    • Answer: End-to-end testing in Vue.js involves testing the complete application workflow. Tools like Cypress or Nightwatch.js can be used for Vue.js end-to-end testing.
25. How can you handle asynchronous code in Vue.js testing?
    • Answer: Asynchronous code in Vue.js testing can be handled using async/await syntax, setTimeout, or the flush-promises library. Vue Test Utils also provides utilities for asynchronous testing.

Vue.js Ecosystem interview question:

26. What is Nuxt.js, and how does it relate to Vue.js?
    • Answer: Nuxt.js is a framework built on top of Vue.js that simplifies the development of universal (server-side rendered) Vue.js applications. It provides features like routing, server-side rendering, and middleware.
27. What is Vue CLI, and how is it used in Vue.js development?
    • Answer: Vue CLI is the official command-line interface for Vue.js. It allows scaffolding new projects, managing dependencies, and providing a development server for Vue.js applications.
28. Explain the purpose of the Vue.js DevTools browser extension.
    • Answer: The Vue.js DevTools browser extension allows developers to inspect and debug Vue.js applications in the browser. It provides a visual representation of the component tree, state, and events.
29. What is the Vue.js transition group, and how is it used?
    • Answer: The Vue.js transition group is a wrapper component that applies transition effects to a group of elements. It is used in conjunction with the v-if or v-for directives to animate elements entering or leaving the DOM.
30. How can you handle state management in Vue.js without using Vuex?
    • Answer: Vue.js provides the provide and inject options to handle state management without using Vuex. Components can provide values, and their descendants can inject them.