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Vue.js Interview Questions and Answers - 2025
Vue.js Interview Questions and Answers
Vue.js - Basics:
1. What is Vue.js?
Vue.js is a progressive JavaScript framework used to build user interfaces and single-page applications (SPAs). Vue.js is designed to be flexible, making it easy to integrate into projects, from simple views to complex web apps, and it focuses on the view layer, allowing developers to focus on building interactive and responsive applications efficiently.
2. What is a Single-Page Application?
Single Page Applications (SPAs) load once and robustly update content, reducing wait time for users. It uses JavaScript to fetch data and update the web page without necessitating to reload everything.
3. What is a component in Vue.js?
How can we create a component?
A component in Vue.js is a reusable piece of code that signifies a part of the user interface.
Components make it simpler to handle complex applications by splitting them down into minor,
controllable pieces.
- Register the component in the Vue instance or another component where you want to use it.
- Use the component in your template with its custom tag.
To make a component in Vue.js, pursue these steps
- Create a new component by defining it with 'template' , 'script' , and 'style'.
- Register the component in the Vue instance or another component where you want to use it.
- Use the component in your template with its custom tag.
4. What are Props in Vue.js?
Props in Vue.js are custom attributes that permit parent components to pass data to child components.
They empower component reusability by producing it possible to handle child components from their parent.
They are specified in the child component and received as arguments from the parent.
5. What is the difference between one-way data binding and two-way data binding in Vue.js?
6. What is a Vue.js Router?
Routing in Vue.js is used to navigate the Vue application,
permitting the formation of single-page applications with multiple views.
Vue Router helps link between the browser’s URL/History and
Vue’s components empowering for certain paths to render whatever
view is linked with it. A Vue router is utilized in making single-page applications.
7. What is a Vue instance? How can we create a Vue instance?
Vue.js instance is the root of all Vue application.
It is JavaScript object formed by the 'Vue' constructor function and assists as
the initiating point for building a Vue application.
Vue instances go through a series of initialization steps. These steps trigger lifecycle hooks, which are functions that allow you to execute code at specific stages. Common hooks include:
- beforeCreate:Instance initialization, data/events not yet available.
- created: Instance created, data/events available, but DOM not yet mounted.
-beforeMount: Before DOM compilation and mounting.
-mounted: DOM compiled and mounted, ready for interaction.
-beforeUpdate: Before data changes trigger DOM updates.
-updated: After DOM updates due to data changes.
-beforeUnmount: Before component unmounting.
-unmounted: Component unmounted and destroyed.
The Vue Instance Lifecycle Hooks
Vue instances go through a series of initialization steps. These steps trigger lifecycle hooks, which are functions that allow you to execute code at specific stages. Common hooks include:
- beforeCreate:Instance initialization, data/events not yet available.
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8. What are Filters in Vue.js?
Vue.js filter is defined as Vue components that offer features called filters
to apply text formatting on any part of the data templates dynamically.
They are mainly applied in 'v-bind' expressions.
Filters can perform tasks like formatting dates, capitalizing text.
9. In Vue.js, what is the purpose of nextTick?
After the data have been set and the DOM changed, the nextTick method is only easy solution to perform a function.
10. How do you handle errors and exceptions in Vue.js applications? application?
In Vue.js, the 'errorCaptured' lifecycle hook permits to control errors
taking place in a component and its child components. For application-wide error handling,
you can apply global error handlers like 'Vue.config.errorHandler' .
11. How do you create custom events in Vue.js?
In Vue.js, custom events are formed applying the '$emit' method within a child component to activate an event.
The parent component listens for this event using the 'v-on' directive or its shorthand '@' .
This grants communication between a child and parent components.
12. Explain Virtual Dom in Vue.js?
In Vue.js, the Virtual DOM (VDOM) is an approach used to upgrade execution when updating web pages.
It works like a blueprint of the real web page's structure, kept in memory.
When a Vue component changes, Vue first update VDOM instead of directly editing the real DOM.
Then, it matches the improved VDOM with the earlier one to figure out the smallest number of changes vital in the real DOM. This method lessens the number of upgrades to the existing web page, forming Vue applications rapid and more responsive, notably with often data changes.
13. Explain Hooks in Vue.js? what are the different built-in Hooks in Vue.js?
Hooks are a new feature introduced in Vue.js 3. Hooks are functions that permit adding
reusable logic to components. They permit managing state, lifecycle events, and side effects
within functional components.
'onMounted' : The 'onMounted' hook enacts directly after the component is mounted onto the DOM. It is best for executing tasks like DOM manipulations or fetching data, assuring these operations happen at the right moment while the component's lifecycle.
'onUnmounted' : The 'onUnmounted' hook initiates just before the component is eliminated from the DOM. It is impeccable for doing cleanup tasks, assuring that any vital operations are done before the component is no longer active in the application
Some of the most typically used hooks include:
'onMounted' : The 'onMounted' hook enacts directly after the component is mounted onto the DOM. It is best for executing tasks like DOM manipulations or fetching data, assuring these operations happen at the right moment while the component's lifecycle.
'onUnmounted' : The 'onUnmounted' hook initiates just before the component is eliminated from the DOM. It is impeccable for doing cleanup tasks, assuring that any vital operations are done before the component is no longer active in the application
14. What is a Key in Vue.js?
In Vue.js, a "key" is a unique attribute used mainly to discover nodes in a list of components rendered utilizing 'v-for' . When Vue renders multiple items with 'v-for' , it uses keys to capably update the DOM elements. Using keys correctly helps Vue efficiently update the DOM by reusing extant elements based on changes in data, rather than re-rendering everything from scratch, thus refining execution and stopping unneeded re-renders.
15. Describe the distinction between 'v-show' and 'v-if' ?
16. What is the difference between '$emit' and '$on' in Vue.js?
17. What is a local component in Vue.js?
Local components are defined inside a specific component and are accessible only within that component or its child components.
18. What is a global component in Vue.js?
A global component in Vue.js is a component that is registered globally, forming it accessible for use in any part of the application. This permits the component to be reused over varied templates without requiring to import it each time.
19. What is the purpose of the 'data' function in Vue components?
The 'data' function is applied to clarify the reactive data properties for a component. Such data properties are part of the component's state and can be acquired in the component. The 'data' function must return an object that covers the properties you seek to be reactive.
20. What is Vue CLI and how is it used?
Vue CLI (Command Line Interface) is a tool for fast support Vue.js projects. This is a command-line utility that permits you to choose from a range of build tools. With Vue CLI, developers can rapidly set up a new project with best practices and modern build tools like Webpack or Vite.
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