react js interview questions:

  1. What is React.js, and what problem does it solve in web development?
    • React.js is a JavaScript library used for building user interfaces (UIs) for web applications. It solves the problem of efficiently updating the user interface in response to changes in application state, by introducing a virtual DOM and a declarative programming model.
  2. Explain the difference between React components and HTML elements.
    • React components are reusable, self-contained pieces of UI that manage their own state and can be composed to build complex UIs. HTML elements are predefined tags that represent different types of content on a web page.
  3. What are the key features of React.js that distinguish it from other JavaScript frameworks?
    • Key features of React.js include the virtual DOM for efficient rendering, JSX for writing HTML-like syntax in JavaScript, component-based architecture for building reusable UIs, and a unidirectional data flow for managing application state.
  4. Describe the concept of virtual DOM in React.js and how it improves performance.
    • React uses it to track changes to the UI and determine the most efficient way to update the real DOM. This improves performance by minimizing DOM manipulation and batch updating changes.

react js interview questions
  1. What is called as JSX in React.js? How does it vary from JavaScript syntaxs?
    • With the help of the JavaScript syntax extension JSX, programmers can write HTML-like code in JavaScript. It differs from regular JavaScript syntax by allowing developers to write UI components more declaratively, making the code easier to read and write.
  2. What is the significance of state and props in React components?
    • A component’s state is its internal data, which is subject to change over time.. Props (short for properties) are inputs to a component that are passed from its parent and remain immutable within the component.
  3. Explain the lifecycle methods in React and when they are invoked.
    • React component lifecycle methods are methods that are invoked at different stages of a component’s life, such as mounting, updating, and unmounting. Examples include componentDidMount, componentDidUpdate, and componentWillUnmount.
  4. How do you handle events in React.js?
    • Events in React.js are handled using synthetic event wrappers provided by React, such as onClick or onChange. These event handlers are attached directly to elements in JSX and can be used to trigger actions in response to user interactions.
  5. Discuss the distinction between React.js’s controlled and uncontrolled components..
    • Controlled components in React.js have their state managed by React and are typically used with form elements where their values are controlled by React. Uncontrolled components, on the other hand, have their state managed by the DOM and are accessed using refs. react js interview questions
  6. What are higher-order components (HOCs) in React, and how are they useful?
    • they are useful for code reuse, abstraction of common logic, and adding features like authentication or data fetching to multiple components.

#react js interview questions THAVAM http500.30