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What is a React component? What are its main elements?

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In this post, we will learn in detail about components, which are the main building blocks of React.js.
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React.js
React interview
React component
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React Components are the main building blocks used in the React library. They are used to create the UI (user interface) and divide the program code into modular and reusable parts. With components, different parts of an application can be managed separately, and repetitive code can be reduced.

Main Elements of React Components

  1. Component Definition:
      • Functional Component: Defined as a function and created using function or an arrow function. For example:
        • function Welcome(props) { return <h1>Hello, {props.name}</h1>; }
      • Class Component: Defined as a class and uses the class keyword. For example:
        • class Welcome extends React.Component { render() { return <h1>Hello, {this.props.name}</h1>; } }
  1. Props:
      • Used to pass data to components from the outside. With props, dynamic values can be given to components.
      • Example:
        • <Welcome name="Sara" />
  1. State:
      • Used to store the internal state of a component. State allows for changes within the component.
      • Example:
        • class Counter extends React.Component { constructor(props) { super(props); this.state = { count: 0 }; } render() { return ( <div> <p>Count: {this.state.count}</p> <button onClick={() => this.setState({ count: this.state.count + 1 })}> Increment </button> </div> ); } }
  1. Lifecycle Methods:
      • Methods related to the component's lifecycle, used during creation, updating, and removal of components. Available in class components, for example: componentDidMount, componentDidUpdate, componentWillUnmount.
  1. Rendering:
      • Specifies how the component is displayed on the screen. In class components, rendering is done through the render method, or through the return statement in functional components.
      • Example:
        • function MyComponent() { return <div>Content here</div>; }
  1. JSX (JavaScript XML):
      • A syntax similar to HTML used in React components, which allows writing HTML-like code within JavaScript.
      • Example:
        • const element = <h1>Hello, world!</h1>;
  1. Event Handling:
      • Components respond to user actions (such as button clicks). Event handlers are added through attributes like onClick, onChange.
      • Example:
        • function handleClick() { alert('Button clicked!'); } function Button() { return <button onClick={handleClick}>Click Me</button>; }

Conclusion

React components are powerful tools for creating and managing the UI. Their main elements include component definition, props and state, lifecycle methods, rendering, JSX, and event handling. These elements allow the software to be divided into modular and reusable parts.
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