ReactJS Interview Questions and Answers

Answer - 31 : - When the application is running in development mode, React will automatically check all props that we set on components to make sure they have correct type. If the type is incorrect, React will generate warning messages in the console. It's disabled in production mode due to performance impact. The mandatory props are defined with isRequired. The set of predefined prop types: i. PropTypes.number ii. PropTypes.string iii. PropTypes.array iv. PropTypes.object v. PropTypes.func vi. PropTypes.node vii. PropTypes.element viii. PropTypes.bool ix. PropTypes.symbol x. PropTypes.any We can define propTypes for User component as below: import React from 'react' import PropTypes from 'prop-types'

Answer - 32 : - Below are the list of main advantages of React, 1.. Increases the application's performance with Virtual DOM. 2. JSX makes code easy to read and write. 3. It renders both on client and server side (SSR). 4. Easy to integrate with frameworks (Angular, Backbone) since it is only a view library. 5. Easy to write unit and integration tests with tools such as Jest.

Answer - 33 : - Apart from the advantages, there are few limitations of React too, 1. React is just a view library, not a full framework. 2. There is a learning curve for beginners who are new to web development. 3. Integrating React into a traditional MVC framework requires some additional configuration. 4. The code complexity increases with inline templating and JSX. 5. Too many smaller components leading to over engineering or boilerplate.

Answer - 34 : - Handling events in React elements has some syntactic differences: 1. React event handlers are named using camelCase, rather than lowercase. 2.. With JSX you pass a function as the event handler, rather than a string.

Answer - 35 : - You should use Webpack's DefinePlugin method to set NODE_ENV to production, by which it strip out things like propType validation and extra warnings. Apart from this, if you minify the code, for example, Uglify's dead-code elimination to strip out development only code and comments, it will drastically reduce the size of your bundle.

Answer - 36 : - React Router is a powerful routing library built on top of React that helps you add new screens and flows to your application incredibly quickly, all while keeping the URL in sync with what's being displayed on the page.

Answer - 37 : - React Router is a wrapper around the history library which handles interaction with the browser's window.history with its browser and hash histories. It also provides memory history which is useful for environments that don't have global history, such as mobile app development (React Native) and unit testing with Node.

Answer - 38 : - The React Intl library makes internalization in React straightforward, with off-the-shelf components and an API that can handle everything from formatting strings, dates, and numbers, to pluralization. React Intl is part of FormatJS which provides bindings to React via its components and API.

Answer - 39 : - Below are the main features of React Intl, 1. Display numbers with separators. 2. Display dates and times correctly. 3. Display dates relative to "now". 4. Pluralize labels in strings. 5. Support for 150+ languages. 6.. Runs in the browser and Node. 7.. Built on standards.

Answer - 40 : -