Answers to the Best 21 Vue JS Interview Questions of 2023

Vue.js is an open-source JavaScript framework designed to help developers create user interfaces (UIs) and single-page applications (SPAs). It is one of the most popular frameworks used for developing UIs and SPAs, along with Angular and React. The main features of Vue.js include its lightweight size, two-way data binding, virtual DOM, and component-based architecture. When deciding which of the three frameworks is best, it is important to consider the project requirements and preferences. Each has its own strengths and weaknesses. It is ultimately up to the developer to determine which framework is best suited for the project. Popular Vue.js interview questions include: What are the main concepts of Vue.js? What is the difference between Vue.js and Angular/React? What are the advantages of using Vue.js? What is the Vue CLI? What is the purpose of using components in Vue.js?

What is Vue JS?

Vue.js is an open-source, progressive JavaScript framework that provides developers with the capability to create dynamic user interfaces. It is one of the most popular frameworks for simplifying web development tasks, as it focuses on the view layer of the application. Its easy integration into large front-end projects makes it a great choice for developers who need to quickly develop a web application or interface.

Vue JS installation is simple. In Vue JS, interactive web interfaces are simple to comprehend and quick to construct for any developer.

The initial version of Vue.js was released in February 2014 and has since garnered a great deal of recognition from developers; as of today, it has garnered more than 197,000 stars and 32,000 forks on GitHub, making it one of the most highly rated and popular frameworks.

What are some of the main features of Vue JS?

Here are some of the main features of Vue JS:

  • Virtual DOM

    Vue.js leverages the use of virtual DOM (Document Object Model) extensively. Rather than directly manipulating the original DOM, Vue.js utilises a copy of the DOM in the form of a JavaScript data structure. This replica DOM is then used to apply changes to the actual DOM, allowing for more efficient and faster updates.

    Every time a variation is made to the program, the JavaScript data structure is altered and compared to the original data structure. This particular feature provides users with a convenient and straightforward way to make modifications to the application.
  • Data Binding

    Utilising the Vue JS binding directive, v-bind, data binding can be utilised to assign values to HTML attributes, modify the style, and attach classes. This directive provides a concise and convenient way to associate data with the view layer, resulting in a more efficient development process.
  • Components

    Components are one of the important features of Vue JS that helps create custom elements, which can be reused in HTML.
  • Event Handling

    V-on is the attribute added to the DOM elements to listen to the events in Vue JS.
  • Animation/Transition

    Vue.js provides developers with an extensive range of techniques to create transitions when HTML elements are added, changed, or removed from the Document Object Model (DOM). The built-in transition component of Vue.js must be wrapped around the relevant element in order to produce the desired transition effect. In addition, developers can easily make the user interface more interactive by integrating third-party animation libraries.
  • Directives

    Vue JS has built-in directives such as v-if, v-else, v-show, v-on, v-bind, and v-model, which perform various actions in the front-end development.
  • Routing

    Navigation between pages is easy with the help of Vue-router.
  • Lightweight

    Vue JS script is lightweight and its performance is also very fast.
  • Vue-CLI

    The Vue JavaScript framework can be easily installed and incorporated into your project using the Vue Command Line Interface (Vue-CLI). This command-line interface allows you to quickly and efficiently build and compile your project, providing you with the essential tools necessary for the successful implementation of Vue.

Basic-level Vue JS interview questions and answers

  1. What do we refer to as a Vue app that is rendered server-side?

    A Vue.js application that has been server-rendered can be referred to as “universal” or “isomorphic”. This terminology implies that most of the application code is capable of running on both the client and server sides.
  2. Does Vue support TypeScript?

    Yes. Vue JS ships TypeScript formal type declarations. This function holds true for Vuex, Vue-router, and Vue core.
  3. What is a component system in Vue JS?

    The component system allows the abstraction of complex programs into smaller, reusable, self-contained units.
  4. What are props in Vue JS?

    Props are a type of component where special attributes can be registered.
  5. How to create the two-way binding on textarea, form input, and select elements?

    The V-Model provides developers with the ability to create two-way binding on textarea, form input, and select elements. This model is able to determine the most suitable approach for updating components according to the type of input. By leveraging the V-Model, developers can effectively streamline the development of their applications.
  6. Which event modifiers are available in Vue JS?

    The list of available event modifiers is as follows:
    1. stop
    2. prevent
    3. capture
    4. self
    5. once
    6. passive
  7. What is matching by dynamic route?

    A route can be identified with a dynamic segment that is signified by a colon (‘:’). This feature allows the route to accept dynamic values, which can be beneficial when transmitting an ID along the route. By utilising this functionality, the route is able to match the dynamic segment and extract the dynamic value.

Intermediate-level Vue JS interview questions and answers

  1. Explain the difference between slots and scoped slots

    A slot in a child component is an empty area which is filled with data supplied by the parent component. When using conventional slots, the properties of child components can only be accessed through the standard slot that was constructed in the parent’s scope.

    On the other hand, a scoped slot enables developers to use the data in the slot content and send data from the child component to the parent scope.
  2. Explain the difference between v-if and v-show.

    In order to determine whether to render a component or not, developers can utilise the v-if and v-show directives. While both directives have the same purpose, they have different behaviours, making them ideal for different use cases.

    Although v-if reduces the initial render time, v-if is not the best solution to frequently show and hide items.

    The V-show directive is advantageous in that it renders the element on the Document Object Model (DOM) and uses Cascading Style Sheets (CSS) to determine whether the element should be visible or not, depending on the result of the expression. As all of the elements are added to the DOM, V-show does not impact the initial rendering cost, unlike V-if. Additionally, compared to V-if, the cost of displaying and hiding an element is lower as elements will not be added or removed from the DOM.
  3. What are functional components?

    Functional components offer an alternative to the traditional component structure, in that they do not require the creation of a component instance and are not subject to the usual component lifecycle. Rather, these components are stateless, rendering only when called upon.

    Rather than relying on an options object, developers are able to craft a functional component by utilising a simple function, which effectively serves as its render function.
  4. Describe Single File Components or SFCs.

    Single File Components are similar to other components. They are self-contained in their own files. Here are some of the benefits of SFCs:
    1. Global definitions: All SFCs are registered globally and given unique names.
    2. Robust templates: Instead of using a single template property like other components, developers can easily create template code in SFCs.
    3. CSS support: SFCs allow developers to apply CSS to the component itself.
    4. Support for preprocessors: SFCs support preprocessors like babel, SAAS, and others.
  5. What is the composition API in Vue JS?

    The composition API has many advantages including improved logic reuse, improved type inference, and more adaptable code organisation.

    The Composition API is a suite of APIs that enables developers to construct Vue components through the utilisation of imported functions instead of the traditional method of specifying options. This API includes features such as:
    1. Reactivity API (ref() and reactive()) – directly create reactive states, computed states, and watchers.
    2. Dependency Injection (provide() and inject()) – leverage Vue’s dependency injection system while using reactivity APIs.
    3. Lifecycle Hooks (onMounted() and onUnmounted()) – hook into the component lifecycle.
  6. What are mixins in Vue JS?

    A mixin object can contain any component option. A component that uses a mixin has all of the mixin’s options ‘blended’ into its own options.
  7. How do you verify if a mutation occurs in Vue JS?

    Mutations are functions that only rely on their input arguments, making them easy to test. Furthermore, mutations can be stored in a store for added convenience. In addition to the default export, these mutations should also be exported as a named export to ensure that they can be accessed in the most efficient manner.

Advanced-level Vue JS interview questions and answers

  1. Why should arrow functions not be utilised in Vue instances when writing lifecycle hooks?

    Arrow functions do not have the capability to declare their own ‘this’ as they are not self-contained. Therefore, the only context in which these functions can be used is the context of their parent function.

    When the arrow function (=>) is used in the Vue app, issues arise since the term “this” does not bind to the Vue instance.

    As a result, developers strongly advise utilising the ordinary function rather than the arrow function.
  2. Mention ways to add animations in a Vue application?

    Vue provides four ways to add animations to an application:
    1. Transition and TransitionGroup – Vue components for handling enter/leave and list transitions.
    2. Class-based animations – animations that trigger the CSS class addition.
    3. State-driven animations – transition effects applied by interpolating values such as a component’s style binding.
    4. Watchers – watchers to animate an element based on a numerical state.
  3. What are plugins in Vue JS?

    Plugins provide a great opportunity for code reuse, just like the composition API. They make it simpler to add functionality at the application level, making the development process more efficient. This Vue JS interview question can be utilised to evaluate a candidate’s familiarity with more complex features of Vue and how they can be implemented to optimise codebase operations.

    Plugins are often utilised to offer functionality in an application. Both objects and functions can be used to define plugins; however, they both share the same requirement of having an install() function exposed. This install() function is utilised to apply the app.use() function, as well as incorporate additional properties.
  4. What is Vue-loader?

    Developers can create single-file components in the Vue format using the webpack loader plugin: Vue-loader.

    The Vue-loader module enables webpack to separate and process each of the three sections of a single component file: template, script, and style. This is achieved through the utilisation of various loader modules such as SASS or SCSS loaders.

    Developers can quickly create apps using .vue files thanks to the configuration.

    The Vue-loader module not only enables static assets to be viewed as module dependencies, but also allows webpack loaders to be employed in order to process them. Notably, when developing with Vue-loader, hot reloading is made available, which is especially advantageous for dynamic web applications.
  5. Describe the best way to maintain state in a Vue application.

    As applications expand in terms of features and codebase, the difficulty of managing state increases. In these cases, using an interconnected network of downstream props and upstream events may not be the most effective solution; instead, it is important to have a centralised management system to keep control over state.

    The recommended paradigm for saving states centrally in the Vue ecosystem is Vuex, which is the official state management library.

    The utilisation of Vuex can facilitate the preservation of a centralised state. Vuex serves as a reactive data store for components, which updates automatically in response to any alterations in state. Furthermore, multiple independent components can draw from the same core state store.
  6. How can you improve the Vue JS app’s performance?

    A Vue application may respond slowly for the following reasons:
    1. You’re relying on many third-party libraries that are misused or too large.
    2. You have many unoptimized and non-compressed photos.
    3. You are not using lazy loading to load your images.
    4. You are not reusing functionalities across your program.
    5. You have many pages and want to load them all at once.

      Fixing these issues will improve the Vue JS app’s performance.
  7. What are some of Vue JS’s most crucial directives?

    Here are a few of Vue JS’s most crucial directives:
    1. V-if inserts or removes DOM elements based on specified phrases.
    2. Only when the expression adjacent to v-if resolves to false, v-else displays content.
    3. V-show is similar to v-if. However, instead of rendering all elements to the DOM, V-show uses the CSS display property to show and hide them.
    4. Developers can use v-for to iterate over items in an array or object.
    5. The v-model is useful for two-way data bindings.

To sum up

These Vue interview questions and answers will help you prepare for a junior and senior-level Vue developer positions.

It is important to recognise that there is not just a single right answer to open-ended Vue interview questions. Interviewers are generally more interested in grasping the reasoning behind your answers. Therefore, it is wise to be prepared to answer questions about the method of your solution.

Please be advised that technical proficiency is an essential component of the recruitment process, but it is not the sole factor that recruiters consider. Work experience and soft skills are also held in high regard and are given equal importance when selecting a successful candidate.

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FAQs

  1. What is Vue JS used for?

    VueJS is a highly favoured front-end tool due to its versatility, as it can be used to create web interfaces and single-page applications, as well as desktop and mobile apps when used in conjunction with an Electron framework. The HTML extensions and JavaScript base of VueJS make it an ideal choice for developers looking to create applications for a variety of platforms.
  2. Is Vue a framework or library?

    Vue JS is a JavaScript framework for creating single-page apps and user interfaces.
  3. Which is best Angular, React or Vue?

    Angular, React, and Vue are all distinct frameworks used to create front-end applications. While they may be interchangeable in some ways, their differences should be taken into consideration when deciding which to use. As such, it is unproductive to compare them and attempt to decide which is better for a particular purpose.

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