Viasat– React JS Interview Questions

Here is the list of React JS Interview Questions which are recently asked in Viasat company. These questions are included for both Freshers and Experienced professionals. Our React JS Training has Answered all the below Questions.

1. What is React?

React is an open-source JavaScript library that is used to develop complex and interactive web and mobile UI. React follows the component-based approach to create reusable and complex UIs from small and isolated pieces of code called components.

2. What are the major features of React?

The main features of React are

JSX, Components.
One-way Data Binding.
Virtual DOM, Simplicity.
Performance.
Speed and flexibility.

3. What is the difference between Element and Component?

React Element is a simple object that describes a DOM node and its attributes or properties. It is an immutable description object and cannot apply any methods on it. React Component is a function or class that accepts an input and returns a React element.

4. How to create components in React?

When creating a React component, the component's name must start with an upper case letter. The component need the extends React.Component statement, this statement creates an inheritance to React.Component, and gives the component access to React. Component’s functions. The component also requires a render() method to returns HTML.

5. When to use a Class Component over a Function Component?

In class components, the render method will be called, whenever the state of the components changes. On the other hand, the Functional components render the UI based on the props. Class Components should be preferred whenever we have the requirement with the state of the component.

6. What are Pure Components?

In React, components are pure if their output is only determined by their inputs ( props ). React provides the Pure Component base class for these class components.

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7. What is state in React?

State is a JavaScript object that stores component's dynamic data and it enables a component to keep track of changes between renders. Because state is dynamic, it is reserved for interactivity so you don't use it for static React projects.

8. What are props in React?

Props are properties of a Component that comes in handy for customization. A prop can be thought of as a parameter, as it changes the behavior (or output) of a component.

9. Why should we not update the state directly?

Mutating state directly can lead to odd bugs, and components that are hard to optimize. Here's an example. As we know, a common way to tune a React component for performance is to make it “pure,” which causes it to only re-render when its props change (instead of every time its parent re-renders).

10. What are synthetic events in React?

A synthetic event is a cross-browser wrapper around the browser's native event. It has the same interface as the browser's native event, including stopPropagation() and preventDefault() , except the events work identically across all browsers.

11. What is inline conditional expressions?

Inline If with Logical && Operator

If it is false, React will ignore and skip it.

Note that returning a false expression will still cause the element after && to be skipped but will return the false expression. In the example below,

<div>0</div> will be returned by the render method.

12. What is Virtual DOM?

The virtual DOM (VDOM) is a programming concept where an ideal, or “virtual”, representation of a UI is kept in memory and synced with the “real” DOM by a library such as React DOM. This process is called reconciliation. They also are considered a part of “virtual DOM” implementation in React.

13. What is React Fiber?

React Fiber is a complete, backwards compatible rewrite of the React core. The goal is to increase its suitability for areas like animation, layout, and gestures. Its headline feature is incremental rendering: the ability to split rendering work into chunks and spread it out over multiple frames.

14. What is JSX?

JSX is a syntax extension to JavaScript that comes with the full power of JavaScript. JSX stands for JavaScript XML. It enables to write HTML in React. JSX makes it easier to write and add HTML in React.

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TOP MNC's REACT JS INTERVIEW QUESTIONS & ANSWERS

Here we listed all React JS Interview Questions and Answers which are asked in Top MNCs. Periodically we update this page with recently asked Questions, please do visit our page often and be updated in React JS.

Viasat React JS Interview Questions