React.js, commonly known as React, is a popular JavaScript library for building user interfaces. It was developed and is maintained by Facebook and a community of individual developers and companies. React is widely used for creating interactive and dynamic web applications, particularly single-page applications (SPAs) and mobile applications.
Key concepts and features in React.js development include
Components
React applications are composed of components, which are self-contained, reusable units of the user interface. Each component encapsulates its own logic, rendering, and state.
Virtual DOM
React uses a virtual representation of the DOM (Document Object Model) to efficiently update and render components. This allows React to minimize DOM manipulation, improving performance.
JSX
JSX (JavaScript XML) is a syntax extension for JavaScript used in React that allows you to write HTML-like code within JavaScript. It’s used to define the structure of your user interface.
Props
Props (short for properties) are a way to pass data from parent to child components. They make components dynamic by allowing them to receive and display different data.
State
React components can have internal state, which is used to manage and respond to changes in a component. Stateful components can re-render based on changes in their state.
Component Lifecycle
React components have a lifecycle with methods like componentDidMount, componentDidUpdate, and componentWillUnmount. These methods enable you to control the behavior of your components at different points in their lifecycle.
Conditional Rendering
You can conditionally render components or elements based on certain conditions, allowing for dynamic user interfaces.
Lists and Keys
React provides the map function for rendering lists of items. Each item in the list should have a unique “key” to help React efficiently update the UI.
Events
React allows you to handle events like user interactions (e.g., button clicks) and manage the resulting behavior using event handlers.
Forms
You can build forms in React and handle user input, including text input, checkboxes, and dropdowns.
Context API
React’s Context API allows you to pass data through the component tree without having to explicitly pass props at every level, making it easier to manage global state.
Hooks
Introduced in React 16.8, hooks are functions that allow you to use state and other React features without writing class components. Common hooks include useState, useEffect, and useContext.
Routing
While React is primarily a library for UI components, you can use libraries like React Router to implement client-side routing for single-page applications.
Testing
React applications can be tested using various testing libraries and tools, such as Jest and React Testing Library.
React Native
React can be used to build mobile applications through React Native, which allows you to write one codebase for both Android and iOS.