What is the useState hook?

useState is a React Hook that lets you add state variables to functional components. It returns the current state value and a function to update it.

When should I use useEffect?

The useEffect hook is used to perform side effects in components, such as fetching data from an API, subscribing to events, or manually updating the DOM.

What are React Hooks?

React Hooks are functions that let you 'hook into' React state and lifecycle features from function components without needing to write a class component.

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React State Management Fundamentals

Understand React State. Learn how to add local, mutable data to your components to make them interactive and respond to user input.

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State Node

Component Interactivity.

State is the engine of interactivity in React. While props are static inputs, state represents the dynamic, changing nature of your application—from user input to data fetched from an API.

1The Re-rendering Engine

When state changes, React schedules a re-render. It calls your component function again, calculates the difference in JSX, and updates only the changed parts of the DOM. This 'State-to-UI' sync is the core magic of React. Remember: Directly mutating state is the #1 cause of bugs. Always use the setter function to ensure React is aware of the change.

2The Async Challenge

React batches state updates for performance. This means multiple calls to setState might happen at once. If your new state depends on the old state (like adding to a total), you must use a functional update. By passing a function to the setter, React guarantees you have the most up-to-date value, even if other updates are pending.