Ans.React.js is a JavaScript library used for building user interfaces, particularly for single-page applications.
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What are the key features of React.js? Ans.Virtual DOM, component-based architecture, one-way data binding, JSX syntax, and reusability are some key features of React.js.
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Explain the concept of Virtual DOM in React.js.Ans.Virtual DOM is a lightweight copy of the real DOM in memory. React uses it to efficiently update the actual DOM, minimizing expensive operations.
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What is JSX in React.js?Ans.JSX is a syntax extension for JavaScript that allows you to write HTML-like code within your JavaScript files in React. It simplifies the process of creating React elements.
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Explain the difference between state and props in React.js.Ans.State is managed within a component and can be changed over time, while props are passed from a parent component to a child component and remain immutable.
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What is a React component? Explain the various types of components in React.Ans.A React component is a reusable, self-contained piece of code that defines the structure and behavior of a UI element. There are two types of components in React: functional and class components.
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How do you create a React component? Ans.React components can be created either as classes (class components) or as functions (functional components).
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What are controlled components in React.js?Ans.Controlled components are form elements whose values are controlled by React and are updated via state. Changes to the component are handled by event handlers.
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What is the purpose of keys in React lists ?Ans.Keys are used to uniquely identify elements in an array-based list in React. They help optimize the rendering performance and enable React to update only the changed elements.
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Explain the concept of "lifting state up" in React.Ans."Lifting state up" refers to the process of moving the state management from a child component to a parent component in order to share the state among multiple child components.
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What is the significance of the componentDidMount lifecycle method?Ans.The componentDidMount method is invoked immediately after a component is mounted. It is often used for performing side effects, such as data fetching or integrating with third-party libraries.
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How do you handle events in React?Ans.Events in React are handled using synthetic event objects, similar to standard DOM events. You can attach event handlers directly to elements using the JSX syntax.
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What is the purpose of the should ComponentUpdate lifecycle method?Ans.The shouldComponentUpdate method allows you to control whether a component should re-render or not. It can be used to optimize performance by preventing unnecessary re-renders.
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Explain the concept of React Fragments.Ans.React Fragments allow you to group multiple elements together without adding extra nodes to the DOM. They are useful when you need to return multiple elements from a component.
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What is the significance of the PureComponent in React ? Ans.PureComponent is a base class for React components that implements a shallow prop and state comparison in the shouldComponentUpdate method. It helps optimize performance by reducing unnecessary re-renders.
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What is React context ? Ans.React context provides a way to share data between components without explicitly passing props through every level of the component tree.
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What is the difference between React and React Native ?Ans.React is a JavaScript library for building user interfaces for web applications, whereas React Native is a framework for building native mobile applications using React.
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How do you handle forms in React ?Ans.In React, form elements can be handled by creating controlled components. The input values are stored in the component's state and are updated via event handlers.
Ans.React hooks are functions that allow you to use state and other React features in functional components. They provide a simpler way to manage component state and lifecycle.
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Explain the purpose of the useEffect hook in React.Ans.The useEffect hook allows you to perform side effects in functional components. It is similar to the componentDidMount, componentDidUpdate, and componentWillUnmount lifecycle methods combined.