Managing state is one of the most important aspects of building web applications with React. State is the data that determines how your components render and behave. React hooks are a new feature that allow you to use state and other React features without writing a class component. In this article, you will learn how to use React hooks to manage state in your web applications.
React hooks are functions that let you access and manipulate state, lifecycle methods, and other React features from function components. They are prefixed with the word "use", such as useState, useEffect, and useRef. You can also create your own custom hooks to reuse stateful logic across different components.
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React hooks are functions that enable functional components to use states, effects and other React features that were previously only available in class components. Hooks were introduced from React version 16.8 to provide a more expressive way to reuse component logic and manage state in functional components.
The useState hook is the simplest way to manage state in a function component. It takes an initial value as an argument and returns an array with two elements: the current state value and a function to update it. You can use the array destructuring syntax to assign them to variables. For example, const [count, setCount] = useState(0) creates a state variable called count with an initial value of 0 and a function called setCount to change it. You can use the setCount function to update the count value in response to user events, such as clicks or inputs.
It is the most important hook provided by React. Because changing the state trigger the react render cycle and all its magic begins
The useEffect hook lets you perform side effects, such as fetching data, updating the document title, or subscribing to an event, in a function component. It takes a function as an argument, which runs after every render by default. You can also pass a second argument, which is an array of dependencies, to specify when the effect should run. For example, useEffect(() => {document.title = `You clicked ${count} times`}, [count]) updates the document title based on the count state variable, and only runs when count changes. You can also return a cleanup function from the effect function, which runs before the next effect or when the component unmounts, to cancel any subscriptions or timers.
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The useEffect hook in React is used to perform side effects in functional components. It have: Effect Function: code that needs to be executed as a side effect. Dependency Array: If the dependencies change between renders, the effect will re-run. If the array is empty, the effect runs only once after the initial render. Cleanup Function: If your effect performs any cleanup, like unsubscribing from a subscription or clearing up resources, you can return a cleanup function. Example: useEffect(() => { // Effect function const fetchData = async () => { }; fetchData(); // Cleanup function return () => { // Code to run when the component is unmounted or before a re-render }; }, []); // Dependency array
The useRef hook lets you create a persistent reference to a value or an element, which does not change between renders. It takes an initial value as an argument and returns an object with a current property, which holds the reference value. You can use the useRef hook to store mutable variables, such as timers or intervals, that do not affect the component's state or output. You can also use the useRef hook to access DOM elements, such as inputs or buttons, by passing the ref object as a prop. For example, const inputRef = useRef(null) creates a ref object that points to the input element, and <input ref={inputRef} /> passes the ref object as a prop to the input element.
Custom hooks are functions that use other React hooks to encapsulate and reuse stateful logic across different components. They follow the same rules as other hooks, such as only calling them at the top level and not inside loops or conditions. They also have to start with the word "use", such as useCounter, useFetch, or useDarkMode. You can return any value from a custom hook, such as state, functions, or effects. For example, function useCounter(initialValue) {const [count, setCount] = useState(initialValue);const increment = () => setCount(count + 1);const decrement = () => setCount(count - 1);return {count, increment, decrement}} creates a custom hook that returns an object with the count state and two functions to increment and decrement it.
Using custom hooks is similar to using built-in hooks. You can import them from another file or define them in the same file as your component. You can then call them inside your function component and use the returned values as you wish. For example, import useCounter from './useCounter';function App() {const {count, increment, decrement} = useCounter(0);return (<div><h1>{count}</h1><button onClick={increment}>+</button><button onClick={decrement}>-</button></div>)} uses the useCounter custom hook to manage the count state and render a simple counter component.