Q.33 What is the significance of the render() method in React components?

The render() method is a required method in React components that returns the JSX elements to be rendered on the screen. It is responsible for generating the component's output.

Report This Question

Q.34 Describe a state in ReactJS

ReactJS provides state which refers to an object which stores data about the component and as component changes; the state also changes over time, with the component being re-rendered. Component or state changes against action by user or system-generated events.

Report This Question

Q.35 How do you handle rendering lists with dynamic content in React?

When rendering lists with dynamic content, you can use JavaScript expressions and map over the data, generating JSX elements dynamically based on the data.

Report This Question

Q.36 Illustrate props in ReactJS

props in ReactJS expand to Properties and is an object storing data related to attribute value for a specific tag. Props data is similar to an HRML attribute. Props are also used to data transfer amongst components and they are passed similar to function arguments.

Report This Question

Q.37 What is the purpose of the Fragment component in React?

The Fragment component allows you to group multiple JSX elements without adding an additional DOM node to the rendered output. It helps improve the structure of the code.

Report This Question

Q.38 What do you understand by a higher-order component in ReactJS?

A higher-order component in ReactJS refers to a higher level component as it is a container for other components so as to make those components re-usable and simple to use. It is primarily used if the components have common logic.

Report This Question

Q.39 How can you conditionally apply CSS classes to elements in React?

In React, you can conditionally apply CSS classes to elements by using the className prop and dynamically assigning the appropriate class name based on certain conditions.

Report This Question

Q.40 List the various stages in life of methods of components in ReactJS

Components in ReactJS undergo various methods during their lifetime and it includes execution of various methods at different stages and is: getInitialState() - before the component creation, componentDidMount() – if the component is rendered and placed on the DOM, shouldComponentUpdate() – if component observes change in the DOM, componentDidUpdate() - after rendering takes place and componentWillUnmount( - before a component is destroyed and unmounted permanently.

Report This Question

Q.41 What is the role of the key prop when rendering lists?

The key prop is used by React to identify individual elements in a list and efficiently update them when the list changes. It helps React reconcile the virtual DOM and minimize re-renders.

Report This Question

Q.42 What is meant by Redux in ReactJS?

Redux in ReactJS refers to a JavaScript library which is open-source and primarily used for managing the application state and developing the UI for the ReactJS application.

Report This Question

Q.43 How can you handle events on dynamically generated elements in a list?

To handle events on dynamically generated elements in a list, you can attach event handlers to the parent component and utilize event delegation. By using the key prop, you can identify the specific element that triggered the event.

Report This Question

Q.44 List components of Redux in ReactJS

The Redux in ReactJS has mainly three components as Store (for holding application state), Action (keeps source information for the store) and Reducer (stores application's state changes against actions sent to the store.)

Report This Question

Q.45 How do you conditionally render components in React?

In React, you can conditionally render components by using conditional statements within the JSX code, determining which component to render based on certain conditions.

Report This Question

Q.46 Describe ReactJS Router

ReactJS Router is an essential utility for developing and managing specific routes for a ReactJS application thus, provides navigation amongst the various components of ReactJS application and to end user as well for navigating in the ReactJS application.

Report This Question

Q.47 How can you style React components?

React components can be styled using CSS, inline styles, CSS-in-JS libraries like Styled Components, or CSS preprocessors like Sass.

Report This Question

Q.48 What is the utility of ReactJS Router?

ReactJS Router provides a centralized storage and management of routes in ReactJS application. It provides a common framework for the structure and behavior of routes in a ReactJS application especially for single-page web applications. Multiple views in a SPA are provided by defining multiple routes.

Report This Question

Q.49 What are inline styles in React?

Inline styles in React allow you to define styles directly within the JSX code using JavaScript objects. They are written as attributes and can accept dynamic values.

Report This Question

Q.50 Why refs are needed in ReactJS?

The ref is not be widely used in a ReactJS application as it return a reference to the element similar to a pointer in C language. It provides a direct method for accessing the DOM element or the specific instance of a component.

Report This Question

Q.51 What is the benefit of using CSS-in-JS libraries like Styled Components?

CSS-in-JS libraries like Styled Components provide a way to write CSS styles directly in your JavaScript code. They offer scoped styles, dynamic styling, and improved code maintainability.

Report This Question

Q.52 Differentiate amongst Shadow DOM and Virtual DOM

The DOM refers to Document Object Model which refers to the web page. Both Shadow DOM and Virtual DOM are applicable for a ReactJS application development. The Shadow DOM is used for variable scoping and CSS in web components but is a provided by the web browser and not browser agnostic. The Virtual DOM on the other hand is a logical concept which is implemented using the various JavaScript libraries above the browser APIs.

Report This Question

Q.53 How do you apply CSS classes to React components?

You can apply CSS classes to React components by using the className prop and assigning a class name as a string value.

Report This Question

Q.54 What do you understand by ReactJS Fiber?

ReactJS or also called as Fiber refers to the new reconciliation engine from React. It is a reimplementation of the core algorithm which was present in the ReactJS v16. Fiber is a drastic improvement as it enhances suitability for animation, layout, gestures and other UI related tasks, pause, abort, or reuse work, assign priority to different update types and new concurrency primitives.

Report This Question

Q.55 What is the purpose of CSS modules in React?

CSS modules allow you to locally scope CSS styles by automatically generating unique class names for each component. This helps prevent style conflicts and improves modularity.

Report This Question

Q.56 What do you think of Lifting State Up in ReactJS?

Lifting State Up in ReactJS refers to the phenomenon which addresses the situation when multiple components have a requirement for sharing same changing data which is done by lifting the shared state to closest common ancestor. Hence, local state in multiple child components is not saved or maintained thus saving overheads and memory.

Report This Question

Q.57 How can you conditionally apply styles to React components?

To conditionally apply styles to React components, you can use JavaScript expressions within the className or style prop to dynamically assign styles based on certain conditions.

Report This Question

Q.58 What is meant by context in ReactJS?

Context in ReactJS is an n essential element needed for data transfer by the component tree and not using props for the purpose by passing it down manually at every level.

Report This Question

Q.59 How can you override default styles of a third-party React component?

You can override the default styles of a third-party React component by using more specific CSS selectors or by using CSS-in-JS techniques to target and modify the component's styles.

Report This Question

Q.60 What do you understand by reconciliation in ReactJS?

Reconciliation in ReactJS refers to the update of actual DOM which has some updates on a specific element. The newly returned element is compared with the previously rendered one and decided for update of the DOM, to be done or not. This whole process of comparing and deciding and finally rendering is Reconciliation in ReactJS.

Report This Question

Q.61 What is the difference between global and local styles in React?

Global styles in React refer to styles that are applied globally across the entire application, while local styles are scoped to specific components or modules. Global styles can be defined in a separate CSS file or using CSS-in-JS libraries.

Report This Question

Q.62 Are exports supported by lazy function in ReactJS?

At present lazy function in ReactJS do not support exports but default exports is supported by the React.lazy function. If there is a requirement of importing exports named modules, then it can be done by creating an intermediate module which reexports it as the default.

Report This Question

Q.63 How do you handle media queries in React for responsive design?

In React, you can handle media queries for responsive design by using CSS media query syntax within the inline styles or by leveraging CSS-in-JS libraries that provide built-in support for media queries.

Report This Question

Q.64 What is meant by fragments in ReactJS?

Fragments in ReactJS is primarily used for grouping multiple children. It is also used for returning multiple elements for a component.

Report This Question

Q.65 How can you optimize CSS in React for better performance?

To optimize CSS in React, you can minimize the use of inline styles, bundle and minify CSS files, leverage CSS modules for local scoping, and utilize techniques like tree shaking to eliminate unused styles from the final bundle.

Report This Question

Q.66 What do you think of portals in ReactJS?

Portals in ReactJS are used for rendering children into a DOM node which is not inside the DOM hierarchy of the parent component but is present outside the DOM hierarchy of the parent component. It uses the ReactDOM.createPortal(child, container) functions for the purpose of rendering children into an external DOM node.

Report This Question

Q.67 How do you debug React applications?

React applications can be debugged using browser dev tools, console logging, using React Developer Tools extension, setting breakpoints in code, and inspecting component state and props.

Report This Question

Q.68 What is the purpose of the React Developer Tools extension?

The React Developer Tools extension is a browser extension that enhances the browser's dev tools with additional features specifically designed for debugging React applications. It provides a visual representation of the component hierarchy and allows inspection of component props and state.

Report This Question

Q.69 How can you debug React components in browser dev tools?

In browser dev tools, you can debug React components by inspecting the component tree, examining component props and state, setting breakpoints in the code, and stepping through the execution flow.

Report This Question

Q.70 How to do static type checking in ReactJS?

Static type checking in ReactJS applications usually is done by using the PropTypes library but for large code bases, static type checkers are to be used like Flow or TypeScript having compile time type checking and auto-completion.

Report This Question

Q.71 How do you use console.log() for debugging in React?

You can use console.log() statements in your React code to log values or messages to the browser console. This helps in understanding the flow of data and detecting potential issues.

Report This Question

Q.72 List the output after using setState() in constructor in ReactJS

Using setState() in constructor in ReactJS not only assigns to the object state but it will also re-render the component and all its children in the ReactJS application.

Report This Question

Q.73 What is the purpose of React error boundaries?

React error boundaries are components that catch JavaScript errors in their child components during rendering, and display a fallback UI instead of crashing the entire application. They help in handling and recovering from errors gracefully.

Report This Question

Q.74 Are render props and higher order components be replaced by Hooks in ReactJS?

No, render props and higher order components should not be replaced by Hooks in ReactJS but it should only be replaced as per requirement. As, render props and higher-order components mostly render a single child whereas Hooks offer a simple way for the purpose by reducing nesting in the DOM tree.

Report This Question

Q.75 How do you set breakpoints in React code for debugging?

You can set breakpoints in React code by adding the debugger; statement in your JavaScript code. When the code execution reaches the breakpoint, the browser's dev tools will pause and allow you to inspect the application state.

Report This Question

Q.76 How components should be named in ReactJS?

Components naming in ReactJS has been specified and also recommended. The naming convention requires naming of the component by reference and not by using displayName.

Report This Question

Q.77 How can you inspect component props and state during debugging?

During debugging, you can inspect component props and state by logging them to the console, using browser dev tools to inspect the component hierarchy, or utilizing the React Developer Tools extension.

Report This Question

Q.78 What do you think of a switching component in ReactJS?

A switching component in ReactJS is used for rendering of multiple components in ReactJS application. It involves usage of an object for mapping the prop values to components.

Report This Question

Q.79 What are common debugging techniques for identifying performance issues in React apps?

Common debugging techniques for identifying performance issues in React apps include using the React Profiler, analyzing component rendering lifecycles, identifying unnecessary re-renders, and optimizing expensive operations such as rendering large lists.

Report This Question

Q.80 What is the reason for passing a function to setState()in ReactJS?

Passing a function to setState()in ReactJS is primarily done as the setState() is an asynchronous and it may not return a correct state without passing a function to setState(). Hence, we pass a function to setState(), having the previous state as an argument to avoid getting the old state value

Report This Question

Q.81 How do you handle and debug asynchronous code in React?

Asynchronous code in React can be handled and debugged by using async/await, promises, or by utilizing the browser dev tools to step through the asynchronous execution and inspect the intermediate states.

Report This Question

Q.82 What do you understand by strict mode in ReactJS?

The strict mode in ReactJS is specifically used for stricter checking of the ReactJS application. Though no extra DOM elements are rendered, it includes many additional checks and warnings for its descendants. It is available in development mode.

Report This Question

Q.83 What are some best practices for debugging React applications?

Some best practices for debugging React applications include reading error messages carefully, using console.log() strategically, understanding the component lifecycle, utilizing browser dev tools effectively, and using debugging tools specifically designed for React, such as React Developer Tools.

Report This Question

Q.84 Describe ReactJS Mixins

ReactJS Mixins provides a mechanism so that different components can possess a common functionality as by using the PureRenderMixin in ReactJS application. It prevents re-rendering of the components

Report This Question

Q.85 What are side effects in React?

Side effects in React refer to any code that produces an effect outside of the component, such as API calls, modifying the DOM, or subscribing to events. They are typically handled in React using the useEffect hook.

Report This Question

Q.86 What is the utility of the Pointer Events in ReactJS?

Pointer Events in ReactJS provides an integrated interface for dealing with multiple input devices and inputs provided by them in ReactJS application. The inputs can be on a desktop hence mouse will apply but on touch mobile only touch will apply and not mouse.

Report This Question

Q.87 What is the purpose of the useEffect hook in React?

The useEffect hook in React is used to handle side effects in functional components. It allows you to perform tasks such as data fetching, subscriptions, or DOM manipulations after rendering and during component lifecycle.

Report This Question

Q.88 Does the ReactJS v16 has support for custom DOM attributes?

Yes, the custom DOM attributes are supported in the ReactJS v16

Report This Question

Q.89 How do you use the useEffect hook in React?

To use the useEffect hook, you pass a callback function as the first argument, which represents the side effect. This function will be executed after the component has rendered. You can also provide a dependency array as the second argument to control when the effect runs.

Report This Question

Q.90 Without calling the setState function, can we re-render a component in ReactJS?

To re-render a component in ReactJS application but not initiating the setState function involves using the forceUpdate() function but it is not recommended as it access data from this.props and this.state for changes in the component's state or props.

Report This Question

Q.91 What is the purpose of the dependency array in the useEffect hook?

The dependency array in the useEffect hook is used to specify the dependencies for the effect. It determines when the effect should be re-run. If the dependencies change, the effect will be re-evaluated.

Report This Question

Q.92 Differentiate amongst ReactJS and ReactDOM

React and ReactDOM have been recently separated due to React Naive, as earlier ReactDOM was part of React. ReactDOM sits between React and the DOM to mount ReactDOM.render() and provide ReactDOM.findDOMNode() for direct DOM element access. For rest, use React for defining and developing custom elements, for lifecycle hooks, etc. React focuses on web and mobile apps but ReactDOM is specific to web apps.

Report This Question

Q.93 How can you handle cleanup in useEffect?

To handle cleanup in useEffect, you can return a cleanup function from the effect. This function will be called before the component unmounts or before the effect is re-run. It can be used to clean up resources like event listeners or canceling subscriptions.

Report This Question

Q.94 List the reason for ReactDOM being separate from ReactJS

ReactDOM was separated from ReactJS due to introduction of React Native.

Report This Question

Q.95 What is the difference between useEffect and useLayoutEffect?

The main difference between useEffect and useLayoutEffect is when they are executed. useEffect runs after the browser has painted the screen, while useLayoutEffect runs synchronously after the DOM has been updated but before the browser repaints.

Report This Question

Q.96 Differentiate amongst setState() and replaceState() methods in ReactJS

setState()method in ReactJS is applied for merger of the current and previous states whereas replaceState() method in ReactJS simply overwrites the current state with the provided state

Report This Question

Q.97 How can you conditionally run an effect in useEffect?

To conditionally run an effect in useEffect, you can use conditional logic within the effect itself, based on the values or state within the component. You can also specify dependencies in the dependency array to control when the effect runs.

Report This Question

Q.98 How state changes are listened in ReactJS?

In ReactJS listening to state changes is accomplished by using the componentDidUpdate lifecycle method. It involves comparison of state and props values with current state. Earlier componentWillUpdate(object nextProps, object nextState) was used.

Report This Question

Q.99 How can you fetch data using the useEffect hook?

To fetch data using the useEffect hook, you can use asynchronous functions or API calls within the effect. It is common to utilize the fetch API or third-party libraries like Axios to perform data fetching.

Report This Question

Q.100 Why props cannot be updated in ReactJS?

props cannot be updated in ReactJS as due to React core philosophy focused on making the props as immutable and top-down thus, a parent can send any prop values to a child but child cannot change the received prop.

Report This Question

Q.101 What is the purpose of the useEffect hook's return statement?

The return statement in the useEffect hook is used for cleanup. If the effect returns a function, React will call that function before applying the next effect or unmounting the component.

Report This Question

Q.102 List the reason for calling the constructor only once in ReactJS

The constructor are called only once in ReactJS due to the fact of assumption by the React's reconciliation algorithm about same position custom component should not be re-rendered

Report This Question

Q.103 How do you optimize the performance of effects in React?

To optimize the performance of effects in React, you can specify dependencies in the dependency array to ensure the effect only runs when necessary. You can also use techniques like debouncing or throttling to prevent excessive re-renders caused by frequent updates.

Report This Question

Q.104 Does the plain ReactJS provides the facility to use async/await

As no but ReactJS can use the async/await by applying the Babel with transform-async-to-generator plug into accomplish the same. The ReactJS Native has Babel init.

Report This Question

Q.105 What is a reducer in React?

In React, a reducer is a function that takes the current state and an action as parameters and returns a new state based on the action. It is typically used in conjunction with the useReducer hook.

Report This Question

Q.106 List some packages for animation in ReactJS

Packages for animation in ReactJS includes: ReactJS Transition Group and ReactJS Motion, both are very popular.

Report This Question

Q.107 How does the useReducer hook work in React?

The useReducer hook is a built-in hook in React that allows you to manage state using a reducer function. It returns the current state and a dispatch function that is used to send actions to the reducer.

Report This Question

Q.108 List React-specific linters

React-specific linters are linters which specifically work with React and ESLint is one of them. It is very popular and widely used with many plugins like eslint-plugin-react to check best practices, fixing issues with accessibility, etc

Report This Question

Q.109 What are the advantages of using reducers in React?

Using reducers in React provides a centralized approach to managing complex state logic. It helps in separating concerns, simplifies state management, and enables predictable state updates.

Report This Question

Q.110 Differentiate amongst ReactJS Router and history library

ReactJS Router and history library are separate and as the ReactJS Router uses history library and actually is a wrapper round it. The history library actually manages interaction with web browser.

Report This Question

Q.111 How do you define a reducer function in React?

A reducer function in React follows a specific structure. It takes the current state and an action as arguments, performs logic based on the action type, and returns a new state.

Report This Question

Q.112 Why push () and replace () methods of history library are needed?

The history library makes use of push () and replace () methods for a specific tasks related to history as the push () method is used for adding a new location and the replace () function updates the current location with the new one in a history instance.

Report This Question

Q.113 What is the purpose of the action in a reducer?

The action in a reducer is an object that describes the type of operation to be performed on the state. It often includes additional data necessary for updating the state.

Report This Question

Q.114 Describe ReactJS Intl

The ReactJS Intl is actually a library which is specifically used for internalization in ReactJS. It has components and offers an API for string, date and number formatting. ReactJS Intl is part of FormatJS.

Report This Question

Q.115 How do you dispatch actions to a reducer in React?

To dispatch actions to a reducer, you use the dispatch function returned by the useReducer hook. You pass an action object to the dispatch function, which triggers the reducer to update the state accordingly.

Report This Question

Q.116 Describe the usage of in ReactJS Intl

The in ReactJS Intl is primarily used for returning elements instead of plain text thus, can't be used for placeholders.

Report This Question

Q.117 Can you have multiple reducers in a React application?

Yes, you can have multiple reducers in a React application. React provides the combineReducers function that allows you to combine multiple reducers into a single root reducer.

Report This Question

Q.118 Illustrate the steps for formatting date in ReactJS Intl

The steps involved for formatting date in ReactJS Intl involves using the injectIntl () higher-order component to access the formatDate() method by props. The method returns the string representation of the formatted date and is also used by FormattedDate instances.

Report This Question

Q.119 How do you handle asynchronous actions in a reducer?

Reducers in React are typically synchronous, so handling asynchronous actions directly within a reducer is not common. Instead, you can dispatch asynchronous actions from components and handle them using middleware libraries like Redux Thunk or Redux Saga.

Report This Question

Q.120 What do you understand by Shallow Renderer for ReactJS testing?

Shallow Renderer for ReactJS testing is used for developing unit test cases in React. Shallow Renderer renders one level deep components with facts assertion without concerned for child component behavior.

Report This Question

Q.121 How can you access the current state in a reducer?

The current state is passed as the first argument to the reducer function. You can access and modify the state within the reducer logic.

Report This Question

Q.122 Describe the TestRenderer package in ReactJS

The TestRenderer package in ReactJS is a rendering package specially meant to render components to pure JavaScript objects without any DOM dependency.

Report This Question

Q.123 What is the difference between useState and useReducer in React?

useState and useReducer are both hooks used for managing state in React. The main difference is that useState is simpler and ideal for managing simple, independent state values, while useReducer is more suitable for complex state logic and managing state transitions based on actions.

Report This Question

Q.124 What is the Context API in React?

The Context API is a built-in feature in React that allows you to share data across components without the need to pass props manually through each level of the component tree.

Report This Question

Q.125 How do you create a context in React?

To create a context in React, you use the createContext function. It returns an object with Provider and Consumer components that can be used to provide and consume the context data.

Report This Question

Q.126 What is the purpose of the Provider component in the Context API?

The Provider component is used to wrap the components that need access to the context data. It accepts a value prop, which provides the data that will be made available to the consuming components.

Report This Question

Q.127 How do you consume a context in React?

You can consume a context in React using the Consumer component or the useContext hook. The Consumer component provides a render prop function, while the useContext hook allows you to access the context directly within a functional component.

Report This Question

Q.128 How can you access the context data within a component?

You can access the context data within a component by either using the Consumer component and providing a render prop function, or by using the useContext hook to retrieve the context value directly.

Report This Question

Q.129 What is the purpose of the defaultValue in the createContext function?

The defaultValue parameter in the createContext function is optional and is used as the initial value of the context if no Provider is found higher up in the component tree.

Report This Question

Q.130 How can you update the context data in React?

The context data can be updated by modifying the value provided by the Provider component. When the value changes, React will re-render the components that consume the context with the updated data.

Report This Question

Q.131 Can you nest contexts in React?

Yes, you can nest contexts in React. By wrapping components with multiple Provider components, you can create a hierarchy of contexts, and each component can consume the appropriate context data.

Report This Question

Q.132 What is the purpose of the contextType property in class components?

The contextType property is used in class components to assign a context object to the this.context property. It allows access to the context data within the class component.

Report This Question

Q.133 How can you optimize performance when using the Context API?

To optimize performance when using the Context API, you can use the shouldComponentUpdate method or React.memo to prevent unnecessary re-renders of components consuming the context. Additionally, you can use memoization techniques to optimize the creation of context values and avoid unnecessary computations.

Report This Question

Q.134 What is a fragment in React?

A fragment is a component in React that allows you to group multiple children elements without introducing an additional DOM node. It helps to avoid unnecessary parent elements when rendering a list or a group of components.

Report This Question

Q.135 How do you create a fragment in React?

In React, you can create a fragment using the empty JSX syntax <>, or by using the component wrapper. Both methods allow you to group multiple elements without adding a wrapping element.

Report This Question

Q.136 What are portals in React?

Portals in React allow you to render a component's content into a different part of the DOM, outside of its parent component's hierarchy. It is useful for rendering content into a different container or at the top level of the document.

Report This Question

Q.137 How do you create a portal in React?

To create a portal in React, you use the ReactDOM.createPortal method. It takes the content you want to render and a target container where you want to render it, specified as a DOM element.

Report This Question

Q.138 What is the purpose of "refs" in React?

Refs in React provide a way to access and interact with the DOM nodes or React components directly. They are useful for accessing input values, triggering imperative animations, or focusing elements.

Report This Question

Q.139 How do you create a "ref" in React?

In React, you can create a "ref" using the React.createRef() method or by using the "callback ref" approach with a function as a ref attribute. Both methods allow you to create a reference that can be assigned to a component or DOM element.

Report This Question

Q.140 How do you access the value of a "ref" in React?

To access the value of a "ref" in React, you can use the .current property of the "ref" object. For example, if ref is your reference object, you can access the value using ref.current.

Report This Question

Q.141 What is the difference between "ref" and "props" in React?

Props (short for properties) are used to pass data from a parent component to its child components. "Refs" are used to access and interact with DOM elements or child components directly from a parent or a container component.

Report This Question

Q.142 How can you forward a "ref" to a child component in React?

You can forward a "ref" to a child component in React using the React.forwardRef function. This allows the child component to receive the "ref" object and pass it down to a specific DOM element or another child component.

Report This Question

Q.143 Can you have multiple "refs" in a React component?

Yes, you can have multiple "refs" in a React component. You can create multiple "ref" objects and assign them to different components or DOM elements within the component hierarchy.

Report This Question

Q.144 How do you send HTTP requests in React?

In React, you can send HTTP requests using various methods such as the built-in Fetch API, the Axios library, or other HTTP client libraries. These methods allow you to make GET, POST, PUT, DELETE, and other types of requests.

Report This Question

Q.145 What is the Fetch API in React?

The Fetch API is a built-in web API in modern browsers that provides a JavaScript interface for making HTTP requests. It is commonly used in React to fetch data from APIs.

Report This Question

Q.146 How do you perform GET requests in React using the Fetch API?

To perform a GET request in React using the Fetch API, you can use the fetch function and provide the URL you want to fetch. It returns a Promise that resolves to the response data.

Report This Question

Q.147 What is Axios and how is it used for making HTTP requests in React?

Axios is a popular JavaScript library used for making HTTP requests. It provides a simple and powerful API for handling requests and responses. In React, you can install Axios and use it to send HTTP requests.

Report This Question

Q.148 How can you handle errors when sending HTTP requests in React?

When sending HTTP requests in React, you can handle errors by using the .catch() method on the Promise returned by the Fetch API or by handling the catch block in Axios. This allows you to handle any error responses or network issues.

Report This Question

Q.149 What are the advantages of using Axios over the Fetch API?

Axios provides additional features compared to the Fetch API, such as request cancellation, request interception, and global request/response handling. It also has better browser compatibility and offers a more consistent API across different environments.

Report This Question

Q.150 How do you handle asynchronous HTTP requests in React?

Asynchronous HTTP requests in React can be handled using async/await syntax with the Fetch API or Axios. By using the async keyword and await keyword, you can write asynchronous code that waits for the request to complete before proceeding.

Report This Question

Q.151 What is the purpose of handling loading and error states when sending HTTP requests in React?

Handling loading and error states when sending HTTP requests in React is important to provide a better user experience. Displaying a loading state informs the user that the request is in progress, while handling errors gracefully helps in error handling and displaying appropriate error messages.

Report This Question

Q.152 How can you send data in the body of a POST request in React?

To send data in the body of a POST request in React, you can pass an object containing the data as the body property in the request. You also need to set the appropriate headers, such as Content-Type: application/json.

Report This Question

Q.153 How can you cancel or abort an HTTP request in React?

With the Fetch API, you can use the AbortController and AbortSignal interfaces to cancel or abort an HTTP request. Axios also provides a built-in cancelation mechanism using the CancelToken and cancel functions. By calling these functions, you can cancel the request before it is completed.

Report This Question

Q.154 What are custom hooks in React?

Custom hooks are functions in React that allow you to reuse stateful logic across multiple components. They provide a way to extract and share common logic without the need for higher-order components or render props.

Report This Question

Q.155 How do you create a custom hook in React?

To create a custom hook in React, you simply define a function that uses React hooks internally. This function can encapsulate any reusable stateful logic or side effects that can be shared across multiple components.

Report This Question

Q.156 What is the naming convention for custom hooks in React?

Custom hooks in React should always start with the prefix "use" to indicate that they follow the rules of hooks. This naming convention is important for ensuring that React recognizes them as hooks and applies the necessary rules.

Report This Question

Q.157 Can custom hooks have their own state?

Yes, custom hooks can have their own state. They can use state hooks such as useState or useReducer to manage their internal state. This allows custom hooks to encapsulate and manage their own stateful logic.

Report This Question

Q.158 How can you share state between components using custom hooks?

Custom hooks can be used to share stateful logic between components. By extracting common stateful logic into a custom hook, multiple components can use that hook to access and update the shared state.

Report This Question

Q.159 Can custom hooks have side effects?

Yes, custom hooks can have side effects. They can use effect hooks such as useEffect or useLayoutEffect to perform side effects such as data fetching, subscriptions, or event listeners. Custom hooks enable encapsulating and reusing side-effect related logic.

Report This Question

Q.160 How can you pass parameters to custom hooks?

Custom hooks can accept parameters like regular functions. You can define the parameters in the custom hook's function signature and pass them when using the hook in a component. This allows customization and flexibility in the reusable logic of the hook.

Report This Question

Q.161 What is the difference between a custom hook and a regular function in React?

A custom hook in React follows the rules of hooks and can use other hooks internally. It allows for the encapsulation and sharing of stateful logic. In contrast, a regular function does not have access to React hooks and cannot manage state or utilize React-specific features.

Report This Question

Q.162 Can custom hooks replace render props or higher-order components?

Yes, custom hooks can be used as an alternative to render props or higher-order components for code reuse. They provide a cleaner and more composable way to share stateful logic and eliminate the need for nested components or prop drilling.

Report This Question

Q.163 How do you test custom hooks in React?

Custom hooks can be tested using the same testing frameworks and tools used for testing React components. You can write unit tests to verify the behavior of the custom hook, including testing the state changes, side effects, and any returned values.

Report This Question

Q.164 How do you handle form submissions in React?

In React, you can handle form submissions by attaching an event handler to the onSubmit event of the element. Inside the event handler, you can access the form data and perform any necessary actions.

Report This Question

Q.165 How do you handle controlled components in React forms?

Controlled components in React forms are components whose values are controlled by React state. You can achieve this by setting the component's value prop and providing an onChange event handler to update the state when the value changes.

Report This Question

Q.166 What are uncontrolled components in React forms?

Uncontrolled components in React forms are components that manage their own state internally, rather than relying on React state. They are typically used when you don't need to perform immediate validation or access the form data upon submission.

Report This Question

Q.167 How do you handle user input validation in React forms?

User input validation in React forms can be done by using conditional rendering or validation libraries. You can check the validity of the input in the event handler or use libraries like Formik or Yup to handle form validation.

Report This Question

Q.168 What is the purpose of the onChange event in React forms?

The onChange event in React forms is triggered when the value of an input field changes. It allows you to capture and handle the user's input and update the state or perform other actions based on the input.

Report This Question

Q.169 How do you handle user input with multiple form fields in React?

To handle user input with multiple form fields in React, you can maintain a separate state value for each input field and update the respective state when the onChange event is triggered. Each input field can be associated with its own event handler.

Report This Question

Q.170 How do you handle checkboxes and radio buttons in React forms?

For checkboxes and radio buttons in React forms, you can use the checked prop to control the state of the checkbox or radio button. By providing an onChange event handler, you can update the state when the checkbox or radio button is clicked.

Report This Question

Q.171 How can you perform form validation before submission in React?

Form validation before submission in React can be done by validating the form data in the event handler of the form's onSubmit event. You can check if the input values meet certain criteria and display error messages or prevent the form submission if validation fails.

Report This Question

Q.172 How can you handle user input with dropdown/select fields in React forms?

To handle user input with dropdown/select fields in React forms, you can use the value prop to control the selected value and provide an onChange event handler to update the state when the selection changes.

Report This Question

Q.173 How do you handle file uploads in React forms?

For file uploads in React forms, you can use the element. By handling the onChange event, you can access the selected file(s) and perform actions such as displaying the file name or uploading the file to a server.

Report This Question

Q.174 What is Redux and how does it work with React?

Redux is a state management library for JavaScript applications, including React. It provides a predictable state container that enables managing application state in a centralized manner. React can interact with Redux using the react-redux library.

Report This Question

Q.175 What is the purpose of Redux middleware?

Redux middleware allows you to modify the behavior of Redux's dispatch function. It provides a way to add extra functionality to the Redux dispatch flow, such as handling asynchronous actions, logging, or routing.

Report This Question

Q.176 How do you handle asynchronous actions in Redux?

Asynchronous actions in Redux are typically handled using middleware such as Redux Thunk or Redux Saga. These middleware allow you to dispatch asynchronous actions that can perform API calls or other asynchronous operations and update the Redux state accordingly.

Report This Question

Q.177 What is Redux Thunk and how does it work?

Redux Thunk is a middleware for Redux that allows you to write action creators that return functions instead of plain action objects. These functions can dispatch multiple actions and perform asynchronous operations before dispatching the final action.

Report This Question

Q.178 What is Redux Saga and how does it work?

Redux Saga is a middleware for Redux that uses ES6 generators to handle asynchronous actions. It allows you to write complex and powerful asynchronous flows using declarative and structured code.

Report This Question

Q.179 How can you dispatch asynchronous actions using Redux Thunk?

To dispatch asynchronous actions using Redux Thunk, you can define action creators that return a function instead of an action object. Inside the function, you can perform asynchronous operations and dispatch actions based on the results.

Report This Question

Q.180 How can you handle side effects in Redux using Redux Saga?

Redux Saga provides a way to handle side effects, such as API calls or listening to browser events, using generator functions called "sagas." Sagas are responsible for managing and coordinating asynchronous actions and handling complex flows.

Report This Question

Q.181 What is the purpose of Redux devtools and how can you use them?

Redux devtools is a browser extension that allows you to inspect and debug the Redux state and actions. It provides features like time-travel debugging, which allows you to replay and inspect previous actions and state changes.

Report This Question

Q.182 How can you integrate Redux with React components?

You can integrate Redux with React components using the react-redux library. It provides the Provider component to wrap your application and make the Redux store available to all components, and the connect function to connect specific components to the Redux store.

Report This Question

Q.183 What are the benefits of using Redux for managing state in React applications?

Redux provides benefits such as a centralized and predictable state management approach, easier debugging and testing, improved scalability for complex applications, and the ability to share state between components without the need for prop drilling.

Report This Question

Q.184 What is authentication in the context of web development?

Authentication is the process of verifying the identity of a user or system. In web development, it typically involves validating user credentials, such as username and password, to grant access to protected resources or functionalities.

Report This Question

Q.185 How can you implement authentication in a React application?

Authentication in a React application can be implemented by integrating with an authentication service or using libraries such as JSON Web Tokens (JWT) or OAuth. React components can handle user input, make API calls to authenticate the user, and store authentication state.

Report This Question

Q.186 What is JWT and how is it used for authentication in React?

JWT (JSON Web Token) is a compact, URL-safe means of representing claims to be transferred between parties. In React, JWTs can be used for authentication by issuing and verifying tokens. The server generates a token upon successful authentication, which the client includes in subsequent requests to access protected resources.

Report This Question

Q.187 What is OAuth and how does it work with React authentication?

OAuth is an open standard for authorization that enables third-party applications to access user resources without sharing sensitive credentials. With React authentication, OAuth can be used to allow users to log in using their existing accounts from providers such as Google, Facebook, or GitHub.

Report This Question

Q.188 What are the common authentication strategies for React applications?

Common authentication strategies for React applications include session-based authentication, token-based authentication (such as JWT), OAuth authentication using provider APIs, and single sign-on (SSO) solutions.

Report This Question

Q.189 How can you secure routes or components in a React application?

Routes or components can be secured in a React application by implementing protected routes. This involves checking the authentication state and redirecting unauthorized users to a login page or showing appropriate error messages.

Report This Question

Q.190 What is the purpose of authentication tokens in React authentication?

Authentication tokens, such as JWTs, are used in React authentication to validate the identity of a user. They are typically generated upon successful authentication and sent with each subsequent request to verify the user's access to protected resources.

Report This Question

Q.191 How can you handle authentication state and store it in a React application?

Authentication state in a React application can be stored in various ways, such as in React state, in browser cookies, or in local storage. The chosen approach depends on factors like security requirements, persistence needs, and token management.

Report This Question

Q.192 What are the security considerations for React authentication?

Security considerations for React authentication include secure transmission of credentials and tokens over HTTPS, protecting against cross-site scripting (XSS) and cross-site request forgery (CSRF), implementing proper session management, and storing sensitive information securely.

Report This Question

Q.193 How can you handle login/logout functionality in a React application?

Login/logout functionality in a React application can be implemented by capturing user input, validating credentials on the server, storing the authentication token, updating the authentication state, and providing a way to log out and clear the token.

Report This Question

Q.194 What is React Router and what is its purpose?

React Router is a library that provides routing capabilities for React applications. Its purpose is to enable navigation and URL routing in a single-page application (SPA), allowing components to be rendered based on the current URL.

Report This Question

Q.195 How do you install and configure React Router in a React application?

React Router can be installed via npm or yarn using the command npm install react-router-dom or yarn add react-router-dom. Once installed, it can be configured by wrapping the application's root component with the component and defining routes using components.

Report This Question

Q.196 What is the difference between and in React Router?

uses the HTML5 History API for clean, client-side URLs, while uses the URL hash fragment. is commonly used in production environments, while is useful in scenarios where server-side configuration is limited.

Report This Question

Q.197 What is React.js and what are its advantages?

React.js is a JavaScript library that is used for building user interfaces. Its advantages include fast rendering, easy component reusability, and the ability to create complex UIs with ease.

Report This Question

Q.198 How do you define routes using React Router?

Routes in React Router are defined using the component. Each component specifies a path and the component to render when that path is matched. Routes can be nested within each other to create a hierarchical structure.

Report This Question

Q.199 What are controlled and uncontrolled components in React?

Controlled components are those where the value is controlled by React, whereas uncontrolled components are those where the value is controlled by the DOM. Controlled components are easier to validate and can provide better user experience.

Report This Question

Q.200 How can you pass parameters to routes in React Router?

Parameters can be passed to routes in React Router by including them as part of the route's path. Parameters are denoted using a colon (:) followed by the parameter name, and they can be accessed within the component using the useParams() hook or the props.match.params object.

Report This Question

Q.201 What is the significance of JSX in React?

JSX is a syntax extension for JavaScript that allows developers to write HTML-like code in their JavaScript files. JSX helps in creating UI components that are easy to read and understand.

Report This Question

Q.202 What is the purpose of the component in React Router?

The component is used for declarative navigation in React Router. It renders an anchor tag that, when clicked, changes the URL and updates the rendered components based on the configured routes, without triggering a full page refresh.

Report This Question

Q.203 What is the difference between props and state in React?

Props are used to pass data from a parent component to a child component, whereas state is used to manage the data within a component. Props are immutable and can only be changed by the parent component, while state can be changed by the component itself.

Report This Question

Q.204 How can you programmatically navigate to a different route in React Router?

React Router provides a history object that allows for programmatic navigation. You can access the history object using the useHistory hook or the withRouter higher-order component (HOC), and then use methods like push() or replace() to navigate to a different route.

Report This Question

Q.205 How does React handle events?

React handles events using a synthetic event system. When an event is triggered, React creates a synthetic event object and passes it to the event handler. This synthetic event is a cross-browser wrapper around the native event object and provides consistent behavior across different browsers.

Report This Question

Q.206 How do you handle route not found (404) errors in React Router?

React Router provides a component that wraps the routes. By placing a with no specified path as the last child of the , you can create a "catch-all" route that matches any unknown URL and render a "404 not found" component.

Report This Question

Q.207 What is the purpose of keys in React?

Keys are used to uniquely identify elements in a list. When an element is added, moved, or removed from a list, React uses keys to determine which element has changed. This helps in reducing the number of re-renders and improving performance.

Report This Question

Q.208 How can you use route nesting and layout components in React Router?

React Router supports route nesting, which allows for creating nested layouts and hierarchies. You can define nested routes by nesting components within each other, enabling the rendering of different layout components based on the current URL.

Report This Question

Q.209 What is a higher-order component in React?

A higher-order component (HOC) is a function that takes a component as an argument and returns a new component with enhanced functionality. HOCs are used for code reuse, abstraction, and composition in React.

Report This Question

Q.210 What are route guards in React Router, and how can you implement them?

Route guards in React Router are used to restrict access to certain routes based on certain conditions, such as authentication status or user roles. They can be implemented by wrapping routes with higher-order components (HOCs) or using custom hooks to check the necessary conditions before rendering the route.

Report This Question

Q.211 What is Redux in React and why is it used?

Redux is a state management library that is commonly used with React. Redux helps in managing the state of a React application in a centralized manner, making it easier to reason about and debug.

Report This Question

Q.212 What is Next.js and what problem does it solve?

Next.js is a popular framework for building React applications with server-side rendering (SSR) and static site generation (SSG) capabilities. It solves the problem of optimizing performance and SEO for React applications by providing server-side rendering out of the box.

Report This Question

Q.213 How does React handle server-side rendering?

React can be used for server-side rendering (SSR) using libraries like Next.js or Gatsby. SSR helps in improving the performance of the initial page load and SEO by generating HTML on the server and sending it to the client.

Report This Question

Q.214 How do you create a new Next.js project?

You can create a new Next.js project by running the command npx create-next-app followed by the desired project name. This command sets up a new Next.js project with the necessary configuration and folder structure.

Report This Question

Q.215 What is React Router and how does it work?

React Router is a library used for routing in React applications. It allows developers to define routes and their corresponding components, and handles the navigation between those routes. React Router uses the browser's history API to update the URL and render the appropriate component based on the current URL.

Report This Question

Q.216 What are the benefits of server-side rendering (SSR) in Next.js?

Server-side rendering in Next.js provides benefits such as improved performance, better SEO, and enhanced user experience. It allows initial rendering on the server and sends the pre-rendered HTML to the client, reducing the time to first render and improving search engine indexing.

Report This Question

Q.217 How do you optimize performance in a React application?

Performance optimization in a React application can be achieved by reducing the number of re-renders, minimizing the size of the bundle, using server-side rendering, and lazy loading components. Other techniques include using React.memo(), shouldComponentUpdate(), and PureComponent to reduce unnecessary re-renders.

Report This Question

Q.218 What is static site generation (SSG) in Next.js?

Static site generation in Next.js is a feature that allows the generation of pre-rendered HTML pages at build time. This enables fast loading times and eliminates the need for server-side rendering on each request.

Report This Question

Q.219 What is the difference between React and Angular?

React is a JavaScript library for building UI components, while Angular is a complete framework for building web applications. React uses a virtual DOM for efficient rendering, while Angular uses a real DOM. React relies on JavaScript for application logic, while Angular uses TypeScript, a superset of JavaScript with static typing.

Report This Question

Q.220 How can you create dynamic pages in Next.js?

Next.js provides dynamic routing capabilities using the [slug] syntax. By creating a file with this syntax (e.g., [slug].js), you can handle dynamic routes and access the dynamic value within the component using the useRouter hook.

Report This Question

Q.221 How does React differ from Vue.js?

React and Vue.js are both JavaScript frameworks for building user interfaces. React is more lightweight and focused on building components, while Vue.js is more opinionated and provides more out-of-the-box functionality. React uses JSX syntax, while Vue.js uses a template-based syntax. React uses a virtual DOM, while Vue.js uses a real DOM.

Report This Question

Q.222 How does Next.js handle data fetching?

Next.js provides several methods for data fetching, including getStaticProps, getStaticPaths, getServerSideProps, and useSWR. These methods allow you to fetch data during the build process, at runtime, or in a client-side context.

Report This Question

Q.223 What is the purpose of Redux Thunk middleware in React?

Redux Thunk is a middleware that allows developers to write asynchronous logic in Redux actions. It enables the action creator to return a function instead of an object, allowing for more complex logic such as API calls or asynchronous behavior.

Report This Question

Q.224 What is the purpose of the _app.js file in Next.js?

The _app.js file in Next.js is a special file that serves as the entry point for the application. It allows you to customize the default behavior of the Next.js app, such as adding global styles or applying layouts to all pages.

Report This Question

Q.225 What are React Hooks and how do they work?

React Hooks are functions that allow developers to use state and other React features in functional components. They were introduced in React 16.8 as a way to simplify state management and provide a way to reuse logic across multiple components. Hooks use closures to maintain state between renders.

Report This Question

Q.226 How can you handle API routes in Next.js?

Next.js provides built-in API routes that allow you to define serverless API endpoints within your Next.js application. You can create an API route by creating a file inside the pages/api directory, and the route will be accessible at /api/your-route.

Report This Question

Q.227 What is the purpose of the useEffect Hook in React?

The useEffect Hook is used to manage side effects in functional components. It replaces the functionality of the componentDidMount, componentDidUpdate, and componentWillUnmount lifecycle methods in class components. The useEffect Hook runs after every render and can be used to perform actions such as fetching data from an API or updating the document title.

Report This Question

Q.228 What is the purpose of the public folder in Next.js?

The public folder in Next.js is used to store static assets that need to be served directly, such as images or fonts. Anything placed in the public folder can be referenced using the / path in your components.

Report This Question

Q.229 How do you handle forms in React?

Form handling in React involves managing the state of the form inputs and handling the form submission. The state of the form inputs can be stored in the component's state or managed using a form library like Formik or React Hook Form. The form submission can be handled using an onSubmit event handler that triggers an API call or updates the state of the application.

Report This Question

Q.230 How can you deploy a Next.js application?

Next.js applications can be deployed to various platforms and hosting providers. Popular options include Vercel, Netlify, and AWS Amplify. Deployment can typically be done by connecting the project repository to the chosen platform and configuring the build and deployment settings.

Report This Question

Q.231 What is the purpose of React Context and how does it work?

React Context is a feature that allows data to be passed down the component tree without having to pass props down through every level. It provides a way to share data between components that are not directly connected in the component tree. React Context works by creating a context object that can be accessed by any component in the tree using the useContext Hook.

Report This Question

Q.232 What is animation in the context of React apps?

Animation in React apps involves adding motion and visual effects to components or elements to enhance the user experience and make the interface more engaging.

Report This Question

Q.233 What is the difference between React Native and React.js?

React.js is a JavaScript library used for building web applications, while React Native is a framework used for building native mobile applications. React Native uses a subset of React syntax and provides a set of native components that can be used to build cross-platform mobile apps. Unlike React.js, React Native does not use the DOM for rendering.

Report This Question

Q.234 How can you animate components in React?

Components in React can be animated using CSS transitions, CSS animations, or JavaScript-based animation libraries such as React Spring, React Transition Group, or Framer Motion.

Report This Question

Q.235 What is the difference between controlled and uncontrolled components in React?

Controlled components in React are those whose value is controlled by React state, and any changes to their value are handled by a change event. Uncontrolled components, on the other hand, maintain their own state and update their value using a ref. Controlled components are more flexible and easier to test, while uncontrolled components are simpler and require less code.

Report This Question

Q.236 What are CSS transitions and how can you use them for animation in React?

CSS transitions allow you to animate property changes smoothly over a specified duration. In React, you can apply CSS transitions by defining transition properties (e.g., transitionProperty, transitionDuration) and updating them dynamically based on component state changes.

Report This Question

Q.237 How do you handle errors in a React application?

Error handling in React can be done using try/catch blocks, error boundaries, or by using a global error handling library like Sentry. Error boundaries are components that catch and handle errors that occur in their child components, preventing the entire application from crashing.

Report This Question

Q.238 What are CSS animations and how can you use them in React?

CSS animations allow you to create complex animations using keyframes and animation properties. In React, you can use CSS animations by applying animation classes to components or elements and triggering those classes based on component state or events.

Report This Question

Q.239 What is the purpose of the useCallback Hook in React?

The useCallback Hook is used to memoize functions in functional components, preventing unnecessary re-renders. It is often used in conjunction with the useEffect Hook to ensure that functions are only re-created when their dependencies change.

Report This Question

Q.240 What is React Spring and how does it enable animation in React?

React Spring is a popular animation library for React that provides a declarative way to animate components using JavaScript-based animations. It allows you to define animations using hooks or components and provides a physics-based animation system.

Report This Question

Q.241 What is the difference between shallow rendering and deep rendering in React testing?

Shallow rendering in React testing involves rendering a component without rendering any of its children, while deep rendering involves rendering the entire component tree. Shallow rendering is faster and more lightweight, but may not catch certain bugs or issues with child components.

Report This Question

Q.242 How can you handle complex animations or sequencing in React apps?

Complex animations or animation sequences in React apps can be handled using animation libraries like React Spring or Framer Motion. These libraries provide APIs to define multiple animations, chain them together, or trigger animations based on different conditions.

Report This Question

Q.243 What is server-side rendering in React and why is it important?

Server-side rendering in React involves rendering the initial HTML on the server and sending it to the client, rather than relying on the client to render the HTML. It is important for performance, as it can reduce the time to first paint and improve search engine optimization.

Report This Question

Q.244 How can you optimize animations for performance in React?

To optimize animations for performance in React, you can use techniques such as minimizing layout changes, using the shouldComponentUpdate or React.memo to prevent unnecessary renders, and leveraging hardware-accelerated properties like transform or opacity.

Report This Question

Q.245 How do you handle authentication in a React application?

Authentication in React can be handled using JSON Web Tokens (JWT), cookies, or session storage. JWTs are often used for stateless authentication, while cookies and session storage are used for stateful authentication. React libraries like Auth0 and Okta can also be used to handle authentication.

Report This Question

Q.246 What are keyframes in CSS animations and how do they work?

Keyframes in CSS animations define the intermediate states of an animation. They allow you to specify styles at different percentages of the animation duration, creating a smooth transition between those states.

Report This Question

Q.247 What is the purpose of React Portals and how do they work?

React Portals are a feature that allows developers to render a component outside of its parent component, while still maintaining the parent-child relationship. They are often used for modal dialogs or tooltips. React Portals work by creating a new DOM node in the body of the document and rendering the component into that node.

Report This Question

Q.248 How can you create interactive animations in React?

Interactive animations in React can be created by using event handlers such as onClick or onHover to trigger animation changes based on user interactions. You can update component state or apply CSS classes to trigger animations accordingly.

Report This Question

Q.249 What is the difference between React Server Components and React Client Components?

React Server Components are a new feature currently in development that allows for server-side rendering of components with real interactivity. They can be thought of as a combination of server-side rendering and client-side rendering. React Client Components, on the other hand, are a proposal for a future feature that would allow components to be shared between the server and the client.

Report This Question

Q.250 How can you test and debug animations in React apps?

Testing and debugging animations in React apps can be done using browser developer tools like Chrome DevTools. You can inspect elements, view animation timelines, and modify styles or animations in real-time to identify and fix issues. Additionally, you can write unit tests to ensure that animations behave as expected under different scenarios.

Report This Question

Q.251 How do you handle performance issues in a large React application?

Performance issues in a large React application can be handled by optimizing component rendering, reducing bundle size, using code splitting and lazy loading, and using tools like React.memo() and shouldComponentUpdate() to prevent unnecessary re-renders.

Report This Question

Q.252 What is the importance of testing in React app development?

Testing is crucial in React app development as it helps ensure the correctness, reliability, and stability of the application. It aids in catching bugs, verifying functionality, and providing confidence when making changes or refactoring code.

Report This Question

Q.253 What is the purpose of React Fiber and how does it work?

React Fiber is a complete rewrite of the React rendering pipeline, designed to improve performance and enable new features like time slicing and concurrent rendering. It works by breaking the rendering process into smaller, incremental steps that can be interrupted and resumed as needed. This allows React to prioritize rendering high-priority components and avoid blocking the UI thread.

Report This Question

Q.254 What are the different types of testing that can be performed in React apps?

The different types of testing in React apps include unit testing, integration testing, component testing, snapshot testing, end-to-end testing, and performance testing.

Report This Question

Q.255 What is the purpose of React Context and when should it be used?

React Context provides a way to share data between components without passing props down the component tree. It should be used when data needs to be accessible by many components at different levels of the tree, or when passing props down the tree becomes too cumbersome.

Report This Question

Q.256 What is unit testing in React and how can it be performed?

Unit testing in React involves testing individual units of code, typically React components, in isolation. It can be performed using testing frameworks like Jest and tools like React Testing Library or Enzyme.

Report This Question

Q.257 What is the difference between Redux and React Context?

Redux is a state management library that provides a global state container, while React Context provides a way to share data between components without passing props down the tree. Redux is more powerful and scalable than React Context, but also requires more setup and boilerplate code.

Report This Question

Q.258 What is the purpose of snapshot testing in React?

Snapshot testing in React involves capturing the rendered output of a component and comparing it to a stored snapshot. It helps detect unintended changes in the component's structure or appearance.

Report This Question

Q.259 How does React handle server-side rendering with data fetching?

React supports server-side rendering with data fetching by using APIs like fetch() or Axios to fetch data on the server, and passing the data to the client as a prop. This ensures that the data is available immediately on the client, without requiring additional API calls.

Report This Question

Q.260 How can you perform integration testing in React apps?

Integration testing in React apps involves testing the interaction and behavior of multiple components or modules together. It ensures that different parts of the application work correctly when integrated.

Report This Question

Q.261 What is the difference between React and React Native?

React is a JavaScript library for building user interfaces on the web, while React Native is a framework for building native mobile applications using React. React Native uses native components and APIs for building mobile UI, while React uses HTML, CSS, and JavaScript for building web UI.

Report This Question

Q.262 What is the role of testing frameworks like Jest in React app testing?

Testing frameworks like Jest provide the infrastructure and tools necessary for testing React apps. They offer features such as test runners, assertion libraries, mocking utilities, and code coverage reporting.

Report This Question

Q.263 What is the purpose of React Hooks and how do they work?

React Hooks are a feature introduced in React 16.8 that allow developers to use state and other React features in functional components. They work by providing a way to use state and other features without writing a class component, using the useState(), useEffect(), and other Hooks provided by React.

Report This Question

Q.264 How can you mock dependencies or external APIs in React app testing?

Dependencies or external APIs can be mocked in React app testing using Jest's mocking utilities. This allows for isolated testing of components without relying on actual network requests or complex dependencies.

Report This Question

Q.265 What is the difference between state and props in React?

State is used to manage data within a component, while props are used to pass data from a parent component to a child component. State can be changed within a component using setState(), while props are read-only within a component.

Report This Question

Q.266 What is end-to-end testing in React and how can it be performed?

End-to-end testing in React involves testing the entire application flow from start to finish, simulating user interactions and verifying the behavior across multiple components and pages. Tools like Cypress or Puppeteer can be used for end-to-end testing.

Report This Question

Q.267 How does React handle user input and form data?

React handles user input and form data using controlled components, which are components whose value is controlled by React state. When a user enters data into a form field, React updates the state and re-renders the component with the new value.

Report This Question

Q.268 What is the purpose of code coverage in React app testing?

Code coverage measures the percentage of code that is executed during testing. It helps identify areas of code that are not covered by tests and provides insights into the overall test effectiveness.

Report This Question

Q.269 What is the difference between class components and functional components in React?

Class components are React components written in the class syntax, while functional components are written in the function syntax. Class components have access to additional features like state and lifecycle methods, while functional components are simpler and more lightweight.

Report This Question

Q.270 How can you automate and run tests in React app development?

Tests in React app development can be automated and run using scripts in the project's build system or by utilizing continuous integration (CI) tools. For example, Jest provides a command-line interface (CLI) to run tests, and CI tools like Travis CI or Jenkins can be configured to execute tests automatically on code changes.

Report This Question

Q.271 How do you optimize the performance of a React application?

React performance can be optimized by minimizing the number of re-renders, reducing bundle size, using code splitting and lazy loading, using shouldComponentUpdate() or React.memo() to prevent unnecessary re-renders, and using the Chrome DevTools to identify and fix performance issues.

Report This Question

Q.272 What are React Hooks?

React Hooks are functions that allow you to use state and other React features in functional components. They provide a way to manage state, handle side effects, and access React's lifecycle methods without writing class components.

Report This Question

Q.273 How does React handle conditional rendering?

React handles conditional rendering by using JavaScript expressions within JSX to conditionally render components or content. If a condition is true, the component or content is rendered, otherwise it is skipped.

Report This Question

Q.274 Why were React Hooks introduced?

React Hooks were introduced to simplify and improve the state management and lifecycle handling in React components. They promote reusability, reduce code duplication, and make it easier to write and test components.

Report This Question

Q.275 What are React portals and how do they work?

React portals provide a way to render children into a different DOM node outside of the parent component's DOM hierarchy. This allows components to render content into other parts of the HTML document, such as modals or popovers, without affecting the parent component's styles or layout.

Report This Question

Q.276 What are the basic built-in Hooks in React?

The basic built-in Hooks in React are useState, useEffect, useContext, useReducer, useCallback, useMemo, useRef, and useImperativeHandle.

Report This Question

Q.277 What is React Fiber and why was it introduced?

React Fiber is a reimplementation of the React core algorithm that was introduced in React 16. It was designed to improve the performance and usability of the framework, specifically by improving the handling of component updates, prioritizing work, and supporting asynchronous rendering.

Report This Question

Q.278 How does the useState Hook work?

The useState Hook allows functional components to manage state. It returns an array with two elements: the current state value and a function to update the state. By calling the update function, React re-renders the component with the new state value.

Report This Question

Q.279 How does React handle animations and transitions?

React can handle animations and transitions using CSS transitions or animations, or by using third-party libraries like React Transition Group or React Spring. Animations and transitions can be triggered by changes in state or props, or by using hooks like useEffect().

Report This Question

Q.280 How does the useEffect Hook work?

The useEffect Hook enables functional components to handle side effects, such as fetching data or subscribing to events. It takes a function as its first argument, which runs after every render, and can optionally return a cleanup function.

Report This Question

Q.281 What is the difference between React and Vue?

React is a JavaScript library for building user interfaces on the web, while Vue is a complete framework for building web applications. React focuses on the view layer of an application, while Vue provides a more comprehensive solution for building applications, including routing, forms, and other features.

Report This Question

Q.282 How does the useContext Hook work?

The useContext Hook allows functional components to access values from a React context. It takes a context object as its argument and returns the current value provided by the nearest component in the component tree.

Report This Question