Top 25 Vue JS interview questions and answers 2023

Vue.js is a popular JavaScript framework used for building user interfaces and single-page applications. It has gained widespread popularity among developers due to its simplicity, versatility, and ease of use. As a result, Vue.js has become a staple in web development, and many companies are now adopting it as their preferred technology. If you are looking to land a job as a Vue.js developer, it is crucial to have a good understanding of the framework and be well-prepared for the interview process. In this blog post, we will discuss some of the common Vue.js interview questions you might face.

1. What is Vue JS and what are its core features?
   
   Vue JS is a progressive JavaScript framework used for building user interfaces. Its core features include reactive and composable view components, a template syntax for building declarative data-driven UIs, two-way data binding, and a simple and flexible API for creating reactive behavior.
   
2. What is the difference between Vue JS and other JavaScript frameworks like Angular and React?
   
   Vue JS is more lightweight and easier to learn than Angular, while offering more flexibility than React. Vue JS also provides better performance than Angular, and has a simpler and more intuitive API.
   
3. What is a Vue instance and how is it created?
   
   A Vue instance is the root of every Vue application, and it’s created by passing an options object to the Vue constructor function. The options object defines the data, methods, computed properties, and other settings that the instance will use.
   
4. What is a Vue template and how is it used in Vue JS?
   
   A Vue template is a piece of markup that defines the structure of a Vue component’s HTML. It can contain directives, data binding expressions, and other Vue-specific syntax that allows it to interact with the Vue instance’s data and methods.
   
5. What are directives in Vue JS and how are they used?
   
   Directives are special attributes that provide declarative syntax for applying behavior to HTML elements in Vue JS. They are prefixed with “v-” and can modify the element’s attributes, manipulate its contents, or bind it to data in the Vue instance.
   
6. What is data binding in Vue JS and how does it work?
   
   Data binding is the process of synchronizing the data in a Vue instance with the HTML that it renders. Vue provides two types of data binding: one-way and two-way. One-way data binding updates the view when the data changes, while two-way data binding updates the data when the view changes.
   
7. What are computed properties in Vue JS and how are they different from methods?
   
   Computed properties are functions in a Vue instance that calculate a value based on its reactive data. They are cached and only re-evaluated when their dependencies change. Methods, on the other hand, are functions that perform an action when called and are not cached.
   
8. What are watchers in Vue JS and how are they used?
   
   Watchers are functions in a Vue instance that observe changes in reactive data and perform a specific action when the data changes. They are useful for responding to changes that cannot be handled by computed properties or methods.
   
9. What is a Vue component and how is it created?
   
   A Vue component is a reusable and modular piece of UI that encapsulates its own HTML, CSS, and JavaScript. It is created by defining a template, data, methods, and other options in a Vue component object.
   
10. What are props in Vue JS and how are they used to pass data between components?
    
    Props are custom attributes that can be passed to a child component from its parent. They allow the parent to communicate with the child by passing data, which the child can use to render its own UI.
11. What is a slot in Vue JS and how is it used?
    
    A slot in Vue JS is a placeholder in a component’s template that can be filled with content from the parent component. This allows for the creation of more flexible and reusable components. Slots are defined in the child component’s template using the “slot” attribute, and can be filled by the parent component using the “slot” element.
    
12. What is a mixin in Vue JS and how is it used?
    
    A mixin in Vue JS is a way to encapsulate reusable functionality and share it across multiple components. A mixin is a JavaScript object that contains properties and methods that can be merged into a component’s options. Mixins are used to reduce duplication and make components more modular.
    
13. What is the difference between global and local registration of Vue components?
    
    Global registration of Vue components makes them available throughout the entire application, while local registration limits their scope to the component in which they are defined. Global components can be defined using the “Vue.component” method, while local components are defined as options in the component’s object.
    
14. What is the Vue router and how is it used?
    
    The Vue router is a library that provides routing functionality for Vue JS applications. It allows for the creation of single-page applications with multiple views and URLs, enabling navigation between different components without reloading the entire page. The Vue router is used by defining routes as components and mapping them to specific URLs.
    
15. What is Vuex and how is it used in Vue JS?
    
    Vuex is a state management library for Vue JS applications. It provides a centralized store where all application state is held, and allows for the management of complex application-level state in a predictable and scalable manner. Vuex is used by defining state, mutations, actions, and getters, and then accessing them from components using the “mapState”, “mapMutations”, “mapActions”, and “mapGetters” helper methods.
    
16. What is the Vue CLI and how is it used to create Vue JS projects?
    
    The Vue CLI is a command-line interface tool that provides a quick and easy way to create, configure, and manage Vue JS projects. It includes a number of useful features, such as project scaffolding, build tool configuration, and plugin management. To create a Vue JS project using the Vue CLI, you can use the “vue create” command and follow the prompts to configure your project.
    
17. What is the difference between the development and production modes in Vue JS?
    
    In development mode, Vue JS applications include additional debugging information and are optimized for ease of development and debugging. In production mode, the application is optimized for performance and does not include the additional debugging information. This makes the application smaller and faster to load.
    
18. What is the purpose of the Vue devtools?
    
    The Vue devtools is a browser extension that provides a set of debugging tools specifically for Vue JS applications. It allows developers to inspect and manipulate the component tree, view component state and props, monitor events and mutations, and debug application performance.
    
19. How is server-side rendering (SSR) achieved in Vue JS?
    
    Server-side rendering in Vue JS involves rendering the application on the server before sending it to the client, as opposed to rendering it entirely on the client-side. This can improve performance and SEO, as the server can send fully rendered HTML to the client instead of sending JavaScript files to be executed. SSR in Vue JS can be achieved using a number of libraries and techniques, such as the Vue SSR library and serverless functions.
    
20. What are the lifecycle hooks in Vue JS and how are they used?
    
    Lifecycle hooks in Vue JS are methods that are called at specific stages in a component’s lifecycle, such as before the component is mounted, or when it is updated or destroyed.
    
21. How can you optimize the performance of a Vue JS application?
    
    It can be done in multiple ways as follows.
    
    • Use lazy-loading for components and resources that are not immediately required.
    • Minimize the number of re-renders by using computed properties, watchers, and conditional rendering.
    • Use asynchronous rendering for long-running tasks.
    • Use Vuex for managing state and avoiding unnecessary re-renders.
    • Use server-side rendering to improve initial load times.
      
22. How can you handle user input validation in Vue JS?
    
    When it comes to handling user input validation in Vue JS, there are several best practices that can be followed. One of these is to use built-in validators or create custom validators to ensure that user input meets certain requirements. In addition, using form input bindings and computed properties can be helpful for displaying validation errors to the user. Another option is to use the v-model directive, which allows for the creation of two-way data bindings for form elements. For more advanced validation needs, it can be useful to utilize third-party libraries like Vee-Validate or vuelidate. By following these practices, Vue JS developers can ensure that their applications are user-friendly and meet the needs of their users.
    
23. What is the difference between v-show and v-if in Vue JS?
    
    In Vue JS, v-show and v-if are both directives that allow for conditional rendering of elements in the template. However, there is an important difference between the two.
    
    v-show toggles the CSS display property of an element based on a condition, but the element remains in the DOM. This means that even if the condition is false, the element still takes up space and affects the layout of the page.
    
    v-if, on the other hand, conditionally renders the element based on a condition and removes it from the DOM when the condition is false. This means that if the condition is false, the element is not included in the page at all and does not affect the layout.
    
24. How can you communicate between child and parent components in Vue JS?
    
    In Vue JS, there are several ways to communicate between child and parent components. Here are some of the most common methods:
    
    Props: A parent component can pass data down to a child component through props. The child component can then use this data to render its template or perform other actions.
    
    Events: A child component can emit events that the parent component can listen for and respond to. This allows the child component to communicate with its parent and trigger actions based on user input or other events.
    
    Vuex: Vuex is a state management pattern and library for Vue JS applications. It provides a centralized store that can be accessed by any component in the application, allowing for easy communication
    
25. What are some common best practices for Vue JS development?
    
    Here are some common best practices for Vue JS development:
    
    • Use the Single Responsibility Principle (SRP): Each component should have a single responsibility and focus on doing one thing well.
    • Use computed properties: Computed properties can improve performance by caching computed values that depend on reactive data.
    • Use watchers sparingly: Watchers can be useful for responding to changes in reactive data, but should be used judiciously to avoid performance issues.
    • Use v-bind and v-on instead of shorthand: Using v-bind and v-on instead of the shorthand syntax can make the code more explicit and easier to read.
    • Use meaningful component names: Giving components meaningful names can make the code easier to understand and navigate.
    • Follow consistent formatting and naming conventions: Consistent formatting and naming conventions can improve code readability and maintainability.
    • Use the Vue devtools: The Vue devtools can be useful for debugging and profiling Vue JS applications.
    • Use version control: Version control can help manage code changes, collaborate with others, and roll back changes if necessary.
      
      By following these best practices, Vue JS developers can create maintainable, performant, and high-quality code.