ReactJS, a popular JavaScript library for building user interfaces, revolves around the concept of components. Components are the building blocks of React applications, allowing developers to create reusable and modular pieces of UI.
What are Components?
In React, a component is a JavaScript class or function that returns a UI piece. Components can be simple, representing a single HTML element, or complex, composed of multiple elements and other components.
In easy words,
If one is familiar with coding, components can be correlated with functions that once defined can be used as many times as needed.
To simplify further, let's say we are building a website that needs multiple cards, in basic HTML, we have to repeat the same code for each card several times, making it messy. Whereas with the help of the react component, we can keep the code clean by defining the card once as a component and using it as many times as needed
Types of Components:
Functional Components: These are simple functions that take props (short for properties) as input and return JSX (JavaScript XML) elements. Functional components are stateless, making them easier to read, test, and maintain.
Class Components: Class components are ES6 classes that extend the React.Component class. They have their own internal state and lifecycle methods. While functional components are preferred for their simplicity, class components are still used in older codebases or when state and lifecycle methods are necessary.
Two inevitable partners of components are props and state.
Props: Props are immutable data passed from parent to child components. They allow components to be customizable and reusable by passing dynamic values. (same as passing values to one function from another function)
State: State is mutable data managed within a component. It represents the current condition of a component and can change over time. When the state changes, React re-renders the component to reflect the updated state. Component Lifecycle:
Class components have a lifecycle consisting of various methods that are invoked at different stages of a component's existence, such as mounting, updating, and unmounting. These methods provide opportunities for performing tasks like fetching data, subscribing to events, or cleaning up resources.
Key Concepts:
JSX: JSX is a syntax extension for JavaScript that allows HTML to be written within JavaScript code. It makes React components more readable and expressive.
Virtual DOM: React uses a virtual DOM to improve performance by minimizing the number of DOM manipulations. When state or props change, React compares the virtual DOM with the real DOM and only updates the changed parts.
Component Composition: React encourages a modular approach to UI development through component composition. Components can be composed to build complex UIs, making the codebase more maintainable and scalable.
Summing up:
Components are the fundamental building blocks of React applications, allowing developers to create reusable and modular UI elements. By understanding the different types of components, props, states, and lifecycle methods, developers can build dynamic and efficient user interfaces with ReactJS.