Vue.js Interview Questions

Vue.js Interview Questions

1) What is Vue.js?/ What do you understand by Vue.js?

Vue.js is a progressive framework of JavaScript used to create Dynamic User Interfaces and single-page applications.

2) Why is Vue.js called a progressive framework?

Vue.js called a progressive framework because it is being changed and developed continually.

3) Why is Vue.js supposed to be a competitor of Angular in upcoming days?

Vue.js is also used to build User Interfaces and single-page applications like Angular. Nowadays, it is evolving very fast, and with time, new libraries and extensions are coming into existence.

Many developers' community is using Vue.js, and the popularity of this JavaScript language is increasing day by day. That's why it is supposed to be a potential competitor of Angular.

4) Who is the founder/ inventor of Vue.js?

Evan you is the founder of Vue.js. He was working at Google on several Angular projects when he founded Vue.js.

5) What is the VUE-resource? How would you install the Vue-Resource?

The VUE-resource is a plug-in for Vue.js. This plug-in is used with Vue.js to make web requests and handle responses, in which XHMLHttpRequests or JSONP is used.

You can use the following yarn or npm command to install VUE-resource:

$ yarn add vue-resource  

$ npm install vue-resource

6) How can you install Vue.js in your project?

You can install Vue.js in your project by using the following 4 methods:

-Yu can use CDN by including <script> tag in HTML file.

-You can install Vue.js by using Node Package Manager (NPM).

-You can install Vue.js using Bower.

-You can also use Vue-cli to setup your project.

7) How can you create an instance of Vue.js?

You can create a new Vue instance by using the Vue function:

var vm = new Vue({  

  // options  

})   

You have to create a new Vue instance when you want to start a Vue application.

8) What are the advantages of using Vue.js?

Following is the list of advantages of using Vue.js:

-Very Small In Size:

One of Vue.js' biggest advantages is that it is very small in size. This exciting JavaScript plug-in is only 18-21KB, so you can download and use it very easily in no time.

-Easy to Understand and Use:

The framework of Vue.js is very easy to understand, and it id one of the reasons for the popularity of this framework. The users can easily add Vue.js to their web project because of its simple structure and develop applications.

-Simple Integration with Existing Applications:

Vue.js framework can be integrated with the existing applications very easily. Vue.js has a lot of components for everything. You can integrate it with any application that is written in JavaScript.

-Flexible in nature:

The flexible nature of Vue.js also makes it easy to understand for the developers of React.js, Angular.js, and any other new JavaScript framework. It provides a lot of flexibility to use virtual nodes to write HTML files, JavaScript files, and pure JavaScript files.

-Components:

You can create reusable custom elements in Vue.js applications.

-Easy & comprehensive documentation:

The documentation of Vue.js is very easy and comprehensive so that developers can develop applications or web pages, only having little knowledge about HTML.

-Virtual DOM:

Vue.js uses virtual DOM similar to other existing frameworks such as ReactJS, Ember, etc. Virtual DOM is a light-weight in-memory tree representation of the original HTML DOM and updated without affecting the original DOM.

-Two-Way Communication:

Vue.js provides two-way communications with its MVVM architecture that makes it very easy to handle HTML blocks.

9) Name some websites which are using Vue.js?

Following is the list of some websites using Vue.js on parts of their projects and applications:

Grammarly

Netflix

Adobe

Facebook

Laracast

Behance

Gitlab

Euronews

Codeship

Livestorm

Xiaomi

Alibaba

Wizzair etc.

10) What is the difference between one-way data flow/ or one-way data binding and two-way data binding?

In one-way data binding or one-way data flow, the view (UI) part of the application does not update automatically. In this model, when the data Model is changed, you need to write some custom code to make it updated every time after the change. The v-bind directive is used for one-way data flow or binding in Vue.js.

On the other hand, in two-way data binding, the view (UI) part of the application is automatically updated when the data Model is changed. The v-model directive is used for two way data binding in Vue.js.

11) What do you understand by components props in Vue.js?

In Vue.js, every component instance has its own isolated scope. So, you cannot directly reference parent data in a child component's template.

Props are used to pass down data to the child components. Props are custom attributes. You can register on a component. When a value is passed to a prop attribute, it becomes a property on that component instance.

12) What is Vuex?

VueX is a state management pattern and library for the Vue.js application. It is used as a centralized store for all the different components in the Vue.js application. Vuex provides some rules to ensure that the state can only be mutated in a predictable fashion. You can get a lot of additional features by integrating Vuex with the official devtool extension of Vue.js.

13) What are filters in Vue.js?

The Filters are functionality provided by Vue.js components that allow you to apply formatting and transformations to your dynamic template data. Filters are used in two places, mustache interpolations, and v-bind expressions. Filters don't change a component data or anything, but they only affect the output.

14) What are the main usages of filters in Vue.js?

Following is the list of main usages of filters in Vue.js:

-Filters are mainly used to filter the data on the DOM level to provide you the data that is still intact in the storage but is represented in the custom specified manner.

-Filters are used to enhance the presentation of the view layer.

-The filters are also reusable.

-You can declare a filter globally and use it on any desirable component.

-Filters facilitate you to format your data at the view level.

15) How can you deploy the Vue.js application?

You can create a project by using the following command:

vue init webpack myproject  

To run your project, run the following command:

npm run build  

After executing the above command, copy index.html and /dist/ folder into your website root directory, and your project will be deployed.

16) What is Vue-loader in Vue.js?

The Vue-loader is a loader module for webpack in Vue.js that is used to write single file components using the .vue file format.

The single-file component contains three sections called template, script, and style. The webpack can extract and process each section using separate loader modules such as the SASS or SCSS loaders. The vue-loader module makes static assets to be treated as module dependencies and enables processing using webpack loaders.

17) What are the most commonly used Directives in Vue.js?

Following is the list of most commonly used directives in Vue.js:

v-show

v-if

v-model

v-else

v-on

18) What is the key in Vue.js?

To render DOM elements more efficiently, Vue.js reuses the elements instead of creating a new element every time. The key is a kind of flag that tells Vue "if the data associated with this child component is moved somewhere else, then move the component along with it to preserve the changes that already exist."

19) How many types of the directive are used in Vue.js?

The following types of directives are used in Vue.js:

General Directives

Literal Directives

Empty Directives

Custom Directives

20) What is a single-file component in Vue.js?

In Vue.js, a single-file component is a file with a .vue extension that contains a Vue component. The single-file component consists of the component's template, logic, and styles, all bundled together in one file. It also contains one <script> block, optional <template> and <style> blocks, and possible additional custom blocks.

21) How to use a single-file component in Vue.js?

To use a single-file component in Vue.js, we have to set up Vue Loader for parsing the file (It is done automatically as a part of a webpack building pipeline). It also supports non-default languages such as Sass or HTML templating languages with pluggable pre-processors.

22) What is $parent property in Vue.js?

In Vue.js, the $parent property is used to access the parent instance from a child. It is similar to the $root property. The $parent property provides direct access, but it makes the application hard to test and debug. In this property, it is very difficult to find out where the mutation comes from.

23) What is $child property in Vue.js?

In Vue.js, the $child property is just like $parent property, but it is used to access the child instance.

24)  What is the difference between slots and scoped slots in Vue.js?

In Vue.js, a slot is a placeholder in a child component filled with content passed from the parent component.

In the slot, the component is compiled in the parent's scope and then passed to the child component. So, it is not possible to use child component properties in a slot's content.

In Scoped slot, you can pass child component data to the parent scope and then use it in slot content.

25) What is the virtual DOM in Vue.js?

In Vue.js, the virtual DOM is a tree-like data structure or a collection of JavaScript objects that represents DOM nodes. Vue.js manage the nodes of the virtual DOM, and that should be rendered on the page. These objects are called "virtual nodes" or VNodes.

26) What is the main purpose of using virtual DOM in Vue.js? / What is the benefit of using virtual DOM in Vue.js?

The virtual DOM's main purpose is to make DOM manipulation faster and more efficient. It becomes very crucial when you have a lot of nodes in your DOM. In this case, updating these nodes is a very expensive task for processing power and resources required. Here, virtual DOM comes into action and makes JavaScript object significantly faster. Vue.js automatically organizes DOM updates in batches to enhance efficiency.

27) How does data flow between components in a Vue.js app?

In Vue.js, the data is passed to child components from the parent component using a prop or a custom attribute. This custom attribute becomes a property on the child component instance. This procedure is called a one-way data flow.

Once the parent component updates a prop value, the child component is automatically updated. The child component can communicate back to the parent via an event, but mutating a property inside a child component should not be done. It does not affect the parent component also unless it is an object or array. When the child component instance emits an event, the parent assigns a handler to that event, and data is passed back to the parent.