Component in React

What Is A Component?

In React, a component is a self-contained, reusable piece of code that defines a portion of the user interface (UI).

Components function similarly to JavaScript functions: they accept inputs, known as "props," and return React elements that describe what should appear on the screen.

Here are the key aspects of React components:

1. Reusability: Components can be reused across your application, enhancing code efficiency and consistency.

2. Encapsulation: Components encapsulate their logic and state, simplifying reasoning and testing of individual application parts.

3. Composition: React components can be nested to build complex UIs, with each responsible for a specific UI segment.

4. Modularity: Components promote a modular code structure, allowing independent development and testing for easier maintenance and scalability.

5. Props: Components receive data and configuration via props, enabling customization of behavior and appearance.

6. Event Handling: Components handle user interactions through event handlers, processing inputs like clicks and changes.

7. State Management: React components manage their state using hooks or class extensions, facilitating dynamic and interactive UIs.

8. Render: Each React component implements a render method or returns JSX, defining its on-screen representation.

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Types Of Component

React offers two primary ways to define components,

Functional Components	Class Components
These are defined as JavaScript functions.	These are defined as JavaScript classes that extend React.Component.
They are simpler and easier to understand.	Class components have been used in older versions of React and are still relevant in some cases, particularly when working with lifecycle methods or for integrating with certain libraries.
They do not have their own internal state. Hence they "dumb components". With the introduction of React hooks (such as useState and useEffect), functional components can manage local state and perform side effects, blurring the line between stateless and stateful components.	They have their own internal state, which can be modified using setState to trigger re-renders and update the UI.
	They have access to lifecycle methods (e.g., componentDidMount, componentDidUpdate) for managing side effects and component behavior.

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Why Function Components Are Preferred?

In modern React development, functional components are often preferred over class components for their simplicity because of the following reasons,

1. Avoiding this: No need to worry about this context, which is often a source of bugs in class components.
2. Hooks Support: Functional components can use hooks like useState, useEffect, etc., to manage state and lifecycle without needing class-based syntax.
3. Improved Code Reusability: Functional components promote code reusability through custom hooks, which allow you to extract and reuse logic across components.
4. Less Boilerplate: No need to write constructors, lifecycle methods, or bind this. Hooks handle most of these efficiently.
5. Better Performance:
   • Less Memory Usage: Functional components use less memory since they don't require the overhead of classes.
   • Faster Rendering: With the useCallback and useMemo hooks, functional components can optimize rendering by memoizing expensive computations and preventing unnecessary re-renders.
6. Future-Proof:
   • React is moving towards functional components as the preferred pattern, and new features are often optimized for them.
   • The React community is increasingly adopting functional components, with libraries and tools being designed around them.

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When To Use A Class Component Over A Function Component?

After the addition of Hooks(i.e. React 16.8 onwards) it is always recommended to use Function components over Class components in React. Because you could use state, lifecycle methods and other features that were only available in class component present in function component too.

But even there are two reasons to use Class components over Function components.

1. If you need a React functionality whose Function component equivalent is not present yet, like Error Boundaries.
2. In older versions, If the component needs state or lifecycle methods then you need to use class component.

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Stateless vs. Stateful Components

Here's a concise comparison between Stateless (Functional) Components and Stateful (Class) Components in React:

Aspect	Stateless Components	Stateful Components
Definition	Do not manage internal state; rely solely on props.	Manage their own internal state to handle dynamic data.
Characteristics	- Simpler and primarily used for presenting static UI elements. - Easier to test and maintain due to their lack of internal state. - With the introduction of Hooks in React 16.8, functional components can now manage state and side effects, blurring the line between stateless and stateful components.	- Responsible for managing and updating state over time. - Useful for handling user events, form inputs, or data fetching. - Typically more complex due to state management responsibilities.
Example Use Case	A button component that receives props like onClick, label, and style but doesn't manage any internal state.	A form component that tracks user input fields and manages form submission state.