Vue JS Interview Questions

Vue JS Interview Questions

On March 7, 2025, Posted by , In Interview Questions, With Comments Off on Vue JS Interview Questions
Vue JS Interview Questions

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Vue.js Interview Questions focus on assessing a candidate’s proficiency in working with one of the most popular JavaScript frameworks used for building interactive user interfaces and single-page applications. As a progressive framework, Vue.js allows developers to create powerful applications with minimal setup, making it a great choice for developers ranging from beginners to experts. During a Vue.js interview, you can expect questions that explore a range of topics, from basic concepts such as Vue’s reactivity system to advanced techniques like Vuex for state management and Vue Router for navigation.

The key to excelling in Vue.js interviews lies in demonstrating a strong understanding of how the framework operates, its core features, and its ecosystem. Interviewers often look for candidates who are not only familiar with Vue’s syntax and capabilities but also understand best practices for building scalable, maintainable applications. By preparing for questions on component lifecycle, Vue directives, and advanced concepts like dynamic component loading and server-side rendering (SSR), you can showcase your ability to create performant and robust applications using Vue.js.

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1. What is Vue.js, and why is it used in web development?

In my experience, Vue.js is a progressive JavaScript framework used for building user interfaces, especially single-page applications. It is designed to be flexible, lightweight, and easy to integrate with other libraries or existing projects. What I like most about Vue.js is that it focuses on the view layer, making it simple to pick up and integrate into projects. It has a reactive data-binding system that helps keep the UI in sync with the data, making it easier to manage the state of the application without writing complex code.

Vue.js is widely used because of its simplicity, reactivity, and scalability. Its design allows developers to build complex applications while keeping the codebase clean and maintainable. For instance, when I work on a small project or a complex application, Vue’s component-based structure allows me to break down the UI into smaller, reusable components, making development faster and more manageable.

2. How does Vue.js differ from other JavaScript frameworks like React or Angular?

Vue.js stands out because of its simplicity and gentle learning curve compared to other frameworks like React and Angular. One of the main differences is that Vue.js provides a more opinionated framework out-of-the-box, which means it has clear guidelines on how to organize code, while React is more flexible and doesn’t enforce much structure. In my experience, this is a benefit when working in teams because everyone follows the same conventions.

Another difference is that Vue uses a more traditional HTML-based templating syntax, which is easier for developers transitioning from HTML and CSS. React, on the other hand, uses JSX, a syntax extension that combines JavaScript and HTML. Angular, while very powerful, is often considered more complex because of its extensive features like dependency injection and TypeScript integration.

The Vue ecosystem is also simpler to integrate into existing projects, whereas React and Angular are often used to build entire projects from scratch. For instance, I’ve found that integrating Vue into an existing project is relatively seamless, especially with the Vue CLI, which offers an easy way to set up and manage projects.

See also: Amazon Angular JS interview Questions

3. What is a Vue instance, and what role does it play in a Vue.js application?

In Vue.js, the Vue instance is the core of every Vue application. It is where all the data, methods, and computed properties are defined. When I create a Vue instance, it binds the DOM with the Vue application’s data, making it reactive. This instance serves as the connection between the application’s data and the DOM, and it manages how the application should behave when data changes.

The Vue instance also plays a critical role in managing components, which are reusable building blocks for the UI. It is the starting point where I can configure things like lifecycle hooks, data properties, methods, and computed properties. Here’s an example of how a basic Vue instance is set up:

new Vue({
  el: '#app',   // The element to mount the instance
  data: {
    message: 'Hello, Vue!'
  }
});

In this example, the Vue instance is created with the new Vue() syntax. The data property defines an initial value for message, which can be used inside the template. This makes the content reactive, so if the message changes, the DOM automatically updates without needing any additional logic.

4. What is the purpose of templates in Vue.js, and how are they structured?

Templates in Vue.js are used to define the HTML structure of a component. They allow me to create dynamic views by binding the DOM to the Vue instance’s data. The main advantage of using templates in Vue.js is that it separates the structure (HTML) from the behavior (JavaScript), making the code cleaner and easier to maintain. The template is a declarative way to describe the user interface and is used alongside the data to render the final output.

In Vue, the template syntax allows me to use directives, like v-if and v-for, to conditionally render elements or loop through data. It also lets me bind attributes and events to data properties and methods using the v-bind and v-on directives. Here’s an example of a simple template:

<div id="app">
  <p>{{ message }}</p> <!-- Binding the data to the template -->
  <button v-on:click="changeMessage">Change Message</button> <!-- Handling events -->
</div>
new Vue({
  el: '#app',
  data: {
    message: 'Hello Vue.js!'
  },
  methods: {
    changeMessage: function() {
      this.message = 'Message Changed!';
    }
  }
});

In this example, the template binds the message property to a paragraph, and when the button is clicked, the changeMessage method updates the value of message. The template structure in Vue.js allows me to easily manage dynamic content without much overhead.

See also: React JS Interview Questions for 5 years Experience

5. How does Vue.js implement data binding, and what are its benefits?

Vue.js implements data binding using a reactive data model, where any changes made to the data are automatically reflected in the DOM. This is achieved through Vue’s reactivity system, which tracks changes to the data and updates the view when necessary. Vue provides both one-way and two-way data binding.

In two-way data binding, changes to the UI, like input fields, automatically update the data, and changes to the data automatically update the UI. This is especially useful when I’m working with forms. The v-model directive in Vue.js makes two-way binding easy to implement. Here’s an example:

<div id="app">
  <input v-model="message" placeholder="Type something">
  <p>You typed: {{ message }}</p>
</div>
new Vue({
  el: '#app',
  data: {
    message: ''
  }
});

In this example, the v-model directive binds the message data property to the input field. As I type in the input field, the message data property updates, and since Vue is reactive, the updated message is instantly displayed in the paragraph. The benefit of this approach is that I don’t need to manually update the UI or manage event listeners; Vue takes care of that automatically.

See also: Basic React JS Interview Questions for beginners

6. What is the virtual DOM, and how does Vue.js utilize it for performance optimization?

The virtual DOM is an in-memory representation of the actual DOM. In Vue.js, whenever the data in the application changes, Vue doesn’t directly update the real DOM. Instead, it first makes changes to the virtual DOM and then compares it with the previous virtual DOM state. This process is called “reconciliation.” After determining what has changed, Vue efficiently updates only the necessary parts of the real DOM, minimizing the number of changes and improving performance.

I’ve found that the virtual DOM helps to avoid unnecessary re-renders and improves the responsiveness of the application. For example, when the data changes in a large application, Vue ensures that only the affected parts of the DOM are updated, instead of re-rendering the entire page. This is especially beneficial in large applications where performance is crucial.

7. What are directives in Vue.js? Can you give examples of common directives?

In Vue.js, directives are special tokens in the markup that allow me to bind behavior to elements. They are prefixed with v- and are used to apply dynamic behavior to the DOM. Some common directives I use in Vue include v-if, v-for, v-bind, and v-on.

For example:

  • v-if is used for conditional rendering:
<div v-if="isVisible">This is visible only if isVisible is true.</div>
  • v-for is used to loop through an array and render elements:
<ul> <li v-for="item in items" :key="item.id">{{ item.name }}</li> </ul>
  • v-bind dynamically binds attributes to data properties:
<img v-bind:src="imageSrc" alt="Dynamic image">
  • v-on binds event listeners to DOM events:htmlCopy code<button v-on:click="incrementCounter">Increment</button>

Directives help keep the logic concise and declarative, allowing me to express dynamic behaviors directly in the template.

See also: Lifecycle Methods in React JS Interview Questions

8. How do Vue components work, and what role do they play in building a Vue.js application?

Vue components are reusable, self-contained units that encapsulate the HTML, CSS, and JavaScript needed for a particular part of the user interface. Components allow me to break down complex applications into smaller, more manageable pieces. I can define a component with its own data, methods, and lifecycle hooks, and use it anywhere in my application.

For example:

Vue.component('my-component', {
  data: function() {
    return {
      message: 'Hello from the component!'
    }
  },
  template: '<div>{{ message }}</div>'
});

Components help keep the application modular, making the code more maintainable. By using components, I can easily reuse UI elements, pass data between them using props, and handle events in a structured way. This modularity is key when building large applications because it keeps the codebase organized and reduces duplication.

9. What are props in Vue.js, and how do they enable communication between components?

Props in Vue.js are custom attributes that allow parent components to pass data down to child components. They act as a way for the parent component to send data into a child component, and the child component can use this data in its template or logic. Props make components reusable and configurable because the data passed can change based on the parent’s state.

Here’s an example of how to pass props between components:

// Parent component
Vue.component('parent', {
  template: '<child :message="parentMessage"></child>',
  data() {
    return {
      parentMessage: 'Hello from the parent!'
    }
  }
});

// Child component
Vue.component('child', {
  props: ['message'],
  template: '<p>{{ message }}</p>'
});

In this case, the parent component passes the parentMessage data as a prop to the child component, and the child displays it. Props make it easy to share data between components and allow for flexible.

See also: Data Binding in AngularJS Interview Questions

10. Can you explain the concept of Vue lifecycle hooks and provide examples of common ones?

In Vue.js, lifecycle hooks are special methods that allow me to run code at specific stages of a component’s life. These stages include creation, mounting, updating, and destruction. I can use lifecycle hooks to perform actions such as fetching data, updating the DOM, or cleaning up resources.

Some of the most common lifecycle hooks I use are:

created: Called after the instance has been created, but before the template is rendered or DOM is updated. I often use this to fetch data or initialize properties.

created() {
  console.log('Component has been created');
}

mounted: Called after the component is mounted to the DOM. It’s useful for interacting with the DOM or external libraries.

mounted() {
  console.log('Component has been mounted');
}

updated: Called after the component’s reactive data changes and the DOM has been updated. I use this hook to handle post-update logic.

updated() {
  console.log('Component has been updated');
}

destroyed: Called just before the component is destroyed. I use this hook for cleanup, like removing event listeners or stopping timers.javascriptCopy code

destroyed() {
  console.log('Component has been destroyed');
}

Each of these hooks provides a specific point in the component’s lifecycle where I can add custom logic to enhance the functionality of my application.

11. What is the purpose of Vue’s v-model directive, and how is it used in forms?

The v-model directive in Vue.js is used for two-way data binding, primarily in forms. It binds the value of an input element to a data property and automatically updates the property when the input changes, and vice versa. This makes it easy to handle user input without needing to manually write event listeners for each form element.

For example, here’s how I would use v-model in a form:

<div id="app">
  <input v-model="message" placeholder="Type something">
  <p>You typed: {{ message }}</p>
</div>
new Vue({
  el: '#app',
  data: {
    message: ''
  }
});

In this example, the input field is bound to the message data property using v-model. As I type into the input, the message property is automatically updated, and the paragraph displays the updated message. This eliminates the need to manually handle input events, streamlining form management in Vue.js.

See also: Infosys FullStack Developer Interview Questions

12. How does Vue.js handle event handling, and what are the key directives involved?

In Vue.js, event handling is straightforward using the v-on directive. This directive is used to listen for events on DOM elements and run methods when those events are triggered. It simplifies event handling by automatically binding event listeners to the DOM elements and handling the associated logic.

For example, I can listen for a click event on a button:

<button v-on:click="incrementCounter">Increment</button>
new Vue({
  el: '#app',
  data: {
    counter: 0
  },
  methods: {
    incrementCounter() {
      this.counter++;
    }
  }
});

In this example, the v-on:click directive listens for a click on the button, and when the event occurs, the incrementCounter method is called, which increments the counter. The shorthand for v-on is @, so the above example can also be written as:

<button @click="incrementCounter">Increment</button>

Vue makes it simple to handle events and execute associated methods directly within the template, reducing the amount of boilerplate code needed.

13. What is a computed property in Vue.js, and how does it differ from a method?

In Vue.js, computed properties are used to define properties that depend on other data properties and automatically update when the dependent data changes. Computed properties are cached based on their reactive dependencies, meaning they are only recalculated when their dependencies change. This makes them more efficient than methods for derived values.

For example:

<div id="app">
  <p>{{ reversedMessage }}</p>
</div>
new Vue({
  el: '#app',
  data: {
    message: 'Hello Vue!'
  },
  computed: {
    reversedMessage() {
      return this.message.split('').reverse().join('');
    }
  }
});

In this example, the reversedMessage computed property returns the reversed string of the message data property. The key difference between computed properties and methods is that computed properties are cached, so if the message doesn’t change, reversedMessage won’t be recalculated. In contrast, methods are recalculated every time they are accessed.

14. Can you explain the concept of Vue.js filters and how they are used?

Filters in Vue.js are used to format data before displaying it in the template. They can be used to format strings, numbers, dates, and other data types. Filters are often used for tasks like currency formatting or converting text to uppercase.

For example, if I wanted to display a price with a dollar sign, I could use a filter like this:

<div id="app">
  <p>{{ price | currency }}</p>
</div>
Vue.filter('currency', function(value) {
  return '$' + value.toFixed(2);
});

new Vue({
  el: '#app',
  data: {
    price: 10
  }
});

In this example, the currency filter adds a dollar sign and formats the price to two decimal places. Filters can be chained and used directly within the template to make data more presentable without changing the underlying data structure.

See also: Tech Mahindra React JS Interview Questions

15. How do you handle routing in a Vue.js application, and what is Vue Router?

In Vue.js, routing is handled using Vue Router, which allows me to navigate between different views or components within a single-page application. Vue Router provides a declarative way to map URLs to components, making it easy to handle navigation without reloading the page.

For example, to set up routing, I first need to install Vue Router and define routes:

import Vue from 'vue';
import Router from 'vue-router';
import HomeComponent from './components/HomeComponent';
import AboutComponent from './components/AboutComponent';

Vue.use(Router);

const router = new Router({
  routes: [
    { path: '/', component: HomeComponent },
    { path: '/about', component: AboutComponent }
  ]
});

new Vue({
  el: '#app',
  router
});

In the template, I use <router-link> to create links between routes:

<router-link to="/">Home</router-link>
<router-link to="/about">About</router-link>

<router-view></router-view>

The <router-view> tag is used to display the component corresponding to the current route. Vue Router provides a simple, effective way to manage navigation in a single-page application, keeping the user experience smooth and without full page reloads.

16. How does Vuex manage state in large applications, and when should you use modules for scalability?

In Vuex, state management is centralized, meaning all the state of the application is stored in a single store, making it easier to track and manage. In large applications, the state can grow significantly, and using Vuex modules becomes essential for maintaining scalability and readability. I divide the store into modules, each representing a part of the application’s state. Each module can have its own state, mutations, actions, and getters. This allows me to keep the store organized and modular, which is particularly useful when working on large applications with many features.

Here’s an example of using Vuex modules:

const store = new Vuex.Store({
  modules: {
    user: {
      state: {
        name: 'John Doe'
      },
      mutations: {
        setName(state, name) {
          state.name = name;
        }
      }
    },
    products: {
      state: {
        items: []
      },
      mutations: {
        setItems(state, items) {
          state.items = items;
        }
      }
    }
  }
});

In this example, I’ve split the state into two modules: user and products. Each module has its own state and mutations, which keeps the store organized as the application grows.

See also: React Redux Interview Questions And Answers

17. Can you explain Vue.js’s reactivity system and how it tracks changes to data?

Vue.js’s reactivity system is built around getter-setter functions that automatically track and update the DOM when the data changes. Vue uses a dependency tracking system to monitor the data and components that depend on it. When I modify the data, Vue detects the change and updates the DOM where necessary.

Vue creates getters and setters for each property in the data object, and when I access or modify a property, Vue tracks the dependency. When the data changes, the system triggers a re-render only for the parts of the application that depend on the modified data.

Here’s an example:

new Vue({
  el: '#app',
  data: {
    message: 'Hello, Vue!'
  },
  computed: {
    reversedMessage() {
      return this.message.split('').reverse().join('');
    }
  }
});

In this example, the reversedMessage computed property depends on the message data property. When message changes, Vue automatically updates the computed property and re-renders the DOM where needed.

18. What strategies would you use to optimize the performance of a large-scale Vue.js application?

When optimizing large-scale Vue.js applications, I focus on several strategies to maintain performance and ensure a smooth user experience. These strategies include:

  • Lazy loading components: I load components only when they are required by using Vue’s async components or Vue Router’s route-based code splitting.
  • Using keep-alive: For components that are frequently used but don’t need to be re-rendered, I use the <keep-alive> wrapper to preserve the component’s state.
  • Optimizing reactivity: I make sure not to overuse reactive properties, especially for large objects, as Vue tracks dependencies which can impact performance.
  • Debouncing and throttling: For events like scroll or resize, I implement debouncing or throttling to limit the frequency of updates.
  • Server-Side Rendering (SSR): For better performance on initial page load and SEO, I consider SSR with Vue or Nuxt.js.

Here’s an example of lazy loading a component in Vue:

const AsyncComponent = () => import('./components/AsyncComponent.vue');

new Vue({
  el: '#app',
  components: {
    AsyncComponent
  }
});

In this example, the AsyncComponent is loaded only when it’s needed, reducing the initial load time.

19. What is dynamic component loading in Vue.js, and how do you implement it for improved performance?

Dynamic component loading in Vue.js allows me to load components dynamically based on conditions or user interaction. By using Vue’s component element with the :is directive, I can conditionally render different components, which reduces the initial load time of the application by not loading all components upfront.

To improve performance, I load only the necessary components based on user actions or route changes, which prevents unnecessary resources from being loaded.

Here’s an example:

<div id="app">
  <button @click="currentComponent = 'componentA'">Component A</button>
  <button @click="currentComponent = 'componentB'">Component B</button>
  <component :is="currentComponent"></component>
</div>
new Vue({
  el: '#app',
  data: {
    currentComponent: 'componentA'
  },
  components: {
    componentA: { template: '<div>Component A</div>' },
    componentB: { template: '<div>Component B</div>' }
  }
});

In this example, based on user clicks, Vue dynamically loads either componentA or componentB, reducing the number of components loaded at any given time.

See also: Deloitte Angular JS Developer interview Questions

20. How does server-side rendering (SSR) work in Vue.js, and in which scenarios would you use it?

Server-Side Rendering (SSR) in Vue.js involves rendering components on the server rather than in the browser. The server generates the HTML content and sends it to the client, which then takes over the application with client-side JavaScript. SSR improves performance by reducing the time it takes for the page to display content, especially on the first load, and it improves SEO by providing search engines with fully rendered HTML.

In scenarios where SEO is important, such as e-commerce sites or blogs, or when the initial loading time is critical, I would use SSR. Nuxt.js is a framework built on top of Vue.js that simplifies the process of setting up SSR.

Here’s an example of setting up a basic SSR app with Nuxt.js:

npx create-nuxt-app my-ssr-app

Nuxt.js handles server-side rendering out of the box, allowing me to focus on the app’s features rather than the configuration. The server renders the page first, improving load times and providing better SEO performance.

21. How does Vuex manage state in large applications, and when should you use modules for scalability?

In large applications, Vuex is essential for managing state in a centralized manner, which helps keep track of data consistency across multiple components. As the application grows, the store can become harder to manage. To scale efficiently, I divide the store into modules. Each module is like a mini-store, with its own state, mutations, actions, and getters. This modular approach makes it easier to manage the state as the application grows, and it also helps in keeping the codebase organized.

In my experience, I use Vuex modules when:

  • The state is becoming too large to manage in a single store.
  • The application has distinct features that need separate management.
  • Teams need to work on different parts of the store independently.

Here’s an example of how to use Vuex modules:

const store = new Vuex.Store({
  modules: {
    user: {
      state: {
        name: 'John'
      },
      mutations: {
        setName(state, name) {
          state.name = name;
        }
      }
    },
    cart: {
      state: {
        items: []
      },
      mutations: {
        addItem(state, item) {
          state.items.push(item);
        }
      }
    }
  }
});

This way, the user and cart modules each handle their own state, making the store more manageable.

See also: Accenture Angular JS interview Questions

22. Can you explain Vue.js’s reactivity system and how it tracks changes to data?

Vue.js’s reactivity system is built on JavaScript’s getter/setter mechanism. When I define a property in the data object, Vue makes it reactive by using Object.defineProperty() to create getters and setters. This allows Vue to track when a property is accessed or modified, and automatically updates the DOM when the data changes.

Here’s how it works:

  • When data is accessed, Vue registers the component as a subscriber.
  • When the data changes, Vue triggers a rerender for all components that depend on that data.

For example:

new Vue({
  data() {
    return {
      message: 'Hello, Vue!'
    };
  },
  computed: {
    reversedMessage() {
      return this.message.split('').reverse().join('');
    }
  }
});

When I change message, Vue re-evaluates the reversedMessage computed property and updates the DOM accordingly. This ensures that my application’s UI stays in sync with the data.

23. What strategies would you use to optimize the performance of a large-scale Vue.js application?

To optimize the performance of large-scale Vue.js applications, I use a variety of techniques:

  • Lazy Loading: I load only the components I need at any given time. This reduces the initial bundle size.
  • Code Splitting: Using Vue Router’s dynamic imports or Webpack, I split the app into smaller chunks, loading only the necessary parts.
  • Keep-Alive: I wrap frequently used components in <keep-alive> to avoid unnecessary re-renders.
  • Avoiding Re-renders: I make use of computed properties and watchers to reduce unnecessary calculations or updates.
  • Debouncing/Throttling: For events like scroll or resize, I implement debouncing to limit how often the event handler is called.

For instance, here’s how to lazy load components with Vue Router:

const routes = [
  {
    path: '/about',
    component: () => import('./components/About.vue')
  }
];

With this approach, the About component is loaded only when the user navigates to the /about route.

See more: TCS AngularJS Developer Interview Questions

24. What is dynamic component loading in Vue.js, and how do you implement it for improved performance?

Dynamic component loading in Vue.js allows me to load components only when they are required, which can significantly improve the initial load time of my application. Vue’s component element with the :is directive is used to conditionally load different components.

This is particularly helpful for large-scale apps, where loading every component upfront would increase the initial bundle size. I can use dynamic imports or lazy loading strategies to improve performance.

For example:

<template>
  <div>
    <button @click="currentComponent = 'ComponentA'">Load Component A</button>
    <button @click="currentComponent = 'ComponentB'">Load Component B</button>
    <component :is="currentComponent"></component>
  </div>
</template>

<script>
export default {
  data() {
    return {
      currentComponent: null
    };
  },
  components: {
    ComponentA: () => import('./ComponentA.vue'),
    ComponentB: () => import('./ComponentB.vue')
  }
};
</script>

In this example, the components ComponentA and ComponentB are loaded only when needed, optimizing the performance of the application by reducing the initial load time.

25. How does server-side rendering (SSR) work in Vue.js, and in which scenarios would you use it?

Server-Side Rendering (SSR) in Vue.js means that instead of generating HTML on the client side, the HTML is pre-rendered on the server and sent to the client. This improves SEO and performance, as the client receives a fully rendered page, making it available for the user almost instantly.

SSR is particularly useful when:

  • SEO is important for your application, as search engines can index the fully rendered HTML.
  • Faster initial loading is required, especially for content-heavy applications.

Vue has an official framework called Nuxt.js that simplifies the process of setting up SSR. It handles the complexity of SSR and provides features like automatic code splitting and static site generation.

Example of setting up SSR with Nuxt.js:

npx create-nuxt-app my-ssr-app

After creating the app, Nuxt automatically configures SSR for you, so you don’t have to worry about manually handling server-side rendering. When a user visits your site, they get a fully rendered page directly from the server, improving the performance and SEO of your application.

See also: Infosys AngularJS Interview Questions

26. How do you handle events in Vue.js?

Vue.js provides a simple and intuitive way to handle events through the v-on directive. This directive listens for DOM events and triggers methods in response. For custom events, I can use $emit in the child component to send events to the parent, which listens to those events using v-on.

Here’s an example of handling an event:

<!-- Parent Component -->
<child-component @custom-event="handleEvent"></child-component>

<!-- Child Component -->
<template>
  <button @click="sendEvent">Click Me</button>
</template>
<script>
export default {
  methods: {
    sendEvent() {
      this.$emit('custom-event', 'Hello from Child!');
    }
  }
};
</script>
new Vue({
  el: '#app',
  methods: {
    handleEvent(message) {
      console.log(message);
    }
  }
});

In this example, when the button in the child component is clicked, it emits a custom event (custom-event) with a message. The parent listens for this event and handles it by calling the handleEvent method. This allows for clear and efficient communication between components.

27. What are computed properties in Vue.js, and how do you use them?

In Vue.js, computed properties are values that are derived from the component’s data. Unlike methods, computed properties are cached based on their dependencies, meaning they are only recalculated when the underlying data changes. This makes computed properties more efficient than methods when dealing with data that needs to be derived repeatedly.

Here’s an example of using computed properties:

<div id="app">
  <p>Original Price: ${{ price }}</p>
  <p>Discounted Price: ${{ discountedPrice }}</p>
</div>
new Vue({
  el: '#app',
  data: {
    price: 100,
    discount: 20
  },
  computed: {
    discountedPrice() {
      return this.price - (this.price * this.discount / 100);
    }
  }
});

In this example, the discountedPrice computed property calculates the discounted price based on the price and discount data properties. This value is cached and only recalculated if price or discount changes, improving performance when used in multiple places.

See also: Accenture Java interview Questions and Answers

28. How do you handle routing in Vue.js?

In Vue.js, routing is typically handled using Vue Router, which is an official router for Vue.js. Vue Router allows me to create different views for my application and navigate between them based on the URL. I use router-link to define navigation links and router-view to display the current view.

Here’s an example of how routing works:

<div id="app">
  <router-link to="/home">Go to Home</router-link>
  <router-view></router-view>
</div>
const routes = [
  { path: '/home', component: { template: '<div>Home Page</div>' } }
];

const router = new VueRouter({
  routes
});

new Vue({
  el: '#app',
  router
});

In this example, when the user clicks the Go to Home link, Vue Router navigates to the /home path and renders the “Home Page” component inside the router-view. This makes it easy to manage multiple views within a single-page application.

29. What are lifecycle hooks in Vue.js?

Lifecycle hooks in Vue.js are methods that allow me to hook into different stages of a component’s life, such as when it is created, mounted, updated, or destroyed. These hooks are useful for performing actions like fetching data, setting up event listeners, or cleaning up resources.

Here’s an example of using lifecycle hooks:

new Vue({
  el: '#app',
  data: {
    message: 'Hello Vue!'
  },
  created() {
    console.log('Component created');
  },
  mounted() {
    console.log('Component mounted');
  },
  updated() {
    console.log('Component updated');
  },
  destroyed() {
    console.log('Component destroyed');
  }
});

In this example, created is called when the component instance is created, mounted is called after the component is inserted into the DOM, updated is triggered when the component’s data changes and it re-renders, and destroyed is invoked when the component is destroyed. These hooks give me fine-grained control over the component’s behavior at different stages.

See also: Infosys React JS Interview Questions

30. What are filters in Vue.js, and how do you use them?

Filters in Vue.js are functions that allow me to format or transform data before it is displayed in the template. Filters are typically used for tasks like formatting dates, numbers, or applying string transformations. I can apply filters directly in the template using the pipe (|) symbol.

Here’s an example of using filters:

<div id="app">
  <p>{{ message | uppercase }}</p>
</div>
Vue.filter('uppercase', function(value) {
  return value.toUpperCase();
});

new Vue({
  el: '#app',
  data: {
    message: 'hello, vue!'
  }
});

In this example, the custom filter uppercase transforms the message to uppercase before it is displayed in the template. Filters are powerful for formatting data without having to modify the original data, keeping templates clean and declarative.

31. How do you manage component communication in Vue.js?

Component communication in Vue.js can be achieved through props and custom events. Props allow data to flow from a parent to a child, while custom events enable a child component to send messages to a parent. For more complex scenarios, I use a central event bus or Vuex for shared state management.

Here’s an example of parent-child communication:

<!-- Parent Component -->
<child-component :parentData="message" @childEvent="handleChildEvent"></child-component>

<!-- Child Component -->
<template>
  <button @click="sendEvent">Send Event</button>
</template>
<script>
export default {
  props: ['parentData'],
  methods: {
    sendEvent() {
      this.$emit('childEvent', 'Data from child');
    }
  }
};
</script>
new Vue({
  el: '#app',
  data: {
    message: 'Hello from Parent'
  },
  methods: {
    handleChildEvent(payload) {
      console.log(payload);
    }
  }
});

In this example, the parent passes the message data to the child via the parentData prop. The child component emits a childEvent when the button is clicked, and the parent listens for it to handle the event. This is the standard approach for component communication in Vue.js.

Conclusion

To wrap up, mastering Vue.js is a powerful asset for developers looking to build dynamic, responsive web applications. The framework’s simplicity and flexibility make it an excellent choice for both small projects and large-scale applications. By understanding the core features such as the reactivity system, component lifecycle, and Vuex state management, developers can tackle complex problems with ease. Additionally, knowing how to optimize performance, handle dynamic components, and implement server-side rendering (SSR) can help developers create high-performance applications that meet modern standards.

Ultimately, Vue.js offers a strong foundation for building interactive user interfaces and single-page applications. By preparing for Vue.js interview questions and deeply understanding its best practices, you’ll not only be ready to tackle any interview but also excel in delivering top-notch solutions. Whether you’re a novice or an experienced developer, mastering these concepts will ensure you stand out in the competitive job market and unlock opportunities to work on exciting, cutting-edge projects.

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