React js Interview Questions

React js Interview questions Download React js Interview questions PDF

React js Interview questions

Angular Js – developed by Google, angular is a typescript based JavaScript application framework. It is also known as Super-heroic JavaScript MVW Framework. It was developed with the motive to encounter the challenges of creating single page applications. There are several versions of angular such as Angular 2+, Angular 2 or ng2. Angular is the rewritten, mostly incompatible successor to AngularJS which means AngularJS is the oldest framework.

React– React was developed by Facebook in March 2013. It is a JavaScript library that is used for building user interfaces. React creates large web applications and also provides speed, scalability, and simplicity.

Vue Js- Launched in February 2014, Vue is the most famous and rapidly growing framework in JS field. Vue is an intuitive, fast and composable MVVM for building interactive interfaces. It is extremely adaptable and several JavaScript libraries make use of this. Vue is also a web application framework that helps in making advanced single page applications.

Arrow functions are extremely important for React operations. It prevents this bugs. Arrow functions make it easier to predict the behavior of this bugs when passed as callbacks. They don’t redefine the value of this within their function body. Hence, prevents bugs caused by the use of this within callbacks.

Higher order components (HOC) is a function that takes component as well as returns a component. It is a modern technique in React that reuses the component logic. However, Higher order components are not a part of React API, per se. These are patterns that emerge from React’s compositional nature. In other words, HOC’s are functions that loop over and applies a function to every element in an array.

React.js is used by web developers for creating large web pages without reloading the entire page. It uses the data and can be changed over time.

The following are the advantages of using React.js-

1- React makes Search engine optimization (SEO)  easy.

2- It is very efficient as it ensures readability and easy maintenance.

3- It gives extraordinary developer tools to web developers and makes Java coding easier for them.

4- UI test cases.

The following are the disadvantages of React-

1- Some major configurations are required for integrating React js with traditional MVC framework such as substituting erb with React js.

2- It is a steep learning process for people who are new to web development world.

Advantages of React Js

  • React.js is extremely efficient: React.js creates its own virtual DOM where your components actually live. This approach gives you enormous flexibility and amazing gain in performance. React.js also calculates what are the changes needed to be made in DOM. This process of React.js avoids expensive DOM operations and make updates in a very client manner.
  • It makes writing Javascript easier: React.js uses a special syntax called JSX, which allows you to mix HTML with Javascript. The user can drop a bit of HTML in the render function without having to concatenate strings, this is another fantastic thing. React.js turns those bits of HTML into functions with a special JSXTransformer.
  • It gives you out-of-the-box developer tools: When you start your journey with React.js, do not forget to install official React.js chrome extension. It makes debugging your application much easier. After you install the extension, you will have a direct look into the virtual DOM as if you were browsing a regular DOM tree in the elements panel. Isn’t it pretty amazing!
  • It’s awesome for SEO: One of the biggest problems with other Javascript frameworks is that they do not search engine friendly. Though there have been some improvements in this area, search engines generally have trouble reading Javascript heavy applications. React.js stands out from the crowd because you can run React.js on the server, and the virtual DOM will be rendered to the browser as a regular web page.
  • UI Test Cases: It is extremely easy to write UI test cases because the virtual DOM system implemented entirely in JS.


Functional components are those components that returns React elements as a result. These are just simple old JavaScript functions. React 0.14 has given a new shortcut for creating simple stateless components that are known as functional components. These components make use of easy JavaScript functions.

Class components – most of the tech-savvy people are more familiar with class components as they have been around the corner for a longer time. These components make use of plain old java objects for creating pages, mixins, etc in an identical way. Using React’s create a class factory method, a literal is passed in defining the methods of a new component.

Controlled component is more advisable to use as it is easier to implement forms in it. In this, form data are handled by React components. A controlled input accepts values as props and callbacks to change that value.

The uncontrolled component is a substitute for controlled components. Here form data is handled by DOM itself. In uncomfortable components, the ref can be used to get the form values from DOM.