20 Essential React concepts that every developer should know

Here are 20 essential React concepts that every developer should know, organized to cover both fundamental and advanced topics:

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1. JSX (JavaScript XML)

JSX allows you to write HTML in JavaScript. It is then compiled to React.createElement calls, which React uses to render elements.

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1. Components

React apps are built using components, which are either class components or functional components. Components can be reusable and can accept props to customize behavior.

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1. Props (Properties)

Props are inputs to components, passed from a parent component. They allow you to pass data and configuration options to child components.

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1. State

State is used to manage dynamic data within a component. It allows a component to react to user input, network responses, etc., by re-rendering when state changes.

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1. Event Handling

React provides synthetic events that normalize events across browsers. You can handle events like clicks, input changes, etc., within your components.

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1. useState Hook

useState is a React hook used in functional components to add state to the component.

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1. useEffect Hook

useEffect allows you to perform side effects in your functional components, like fetching data, subscribing to external events, and manually changing the DOM.

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1. Conditional Rendering

React enables you to conditionally render UI based on the state or props of the component, typically using if, ternary operators, or logical &&.

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1. Lists and Keys

Rendering lists of items in React involves using the .map() function. Each list item should have a unique key prop to help React identify which items have changed.

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1. Component Lifecycle (Class Components)

For class components, lifecycle methods like componentDidMount, componentDidUpdate, and componentWillUnmount allow you to run code at specific stages of the component’s lifecycle.

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1. React Router

React Router is a declarative routing library that allows you to navigate between different pages (or views) in a single-page application (SPA).

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1. Forms and Controlled Components

In React, form elements (like input fields) are often "controlled", meaning their values are bound to the component state, making them easier to manage.

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1. Context API

The Context API allows you to manage global state (e.g., themes, authentication) and share it across the component tree without passing props manually through each level.

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1. useContext Hook

The useContext hook provides a way to access values from the Context API in functional components, making it easier to consume context values.

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1. Error Boundaries

Error boundaries are React components that catch JavaScript errors anywhere in their child component tree and display a fallback UI.

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1. React Memoization (React.memo)

React.memo is a higher-order component used to memoize the output of a component, preventing unnecessary re-renders when the props haven’t changed.

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1. Higher-Order Components (HOCs)

HOCs are functions that take a component and return a new component with added functionality, enabling code reuse.

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1. useCallback and useMemo Hooks

useCallback memoizes a function so that it isn’t recreated on every render, while useMemo memoizes the result of an expensive calculation.

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1. Lazy Loading and Suspense

Lazy loading allows you to load components only when needed to improve performance. Suspense allows you to show a fallback UI while waiting for lazy-loaded components.

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1. Code Splitting

Code splitting allows you to split your React app’s JavaScript bundle into smaller parts, improving load time and performance by loading only the required parts when needed.

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These concepts form the foundation of building efficient and maintainable React applications. Understanding and using them well will help you become a proficient React developer.