Science Knowings: JavaScript Course For Social Media

useState Hook

1. useState Hook - Introduction

Welcome to the useState Hook!

In this session, we'll dive into the world of state management with useState Hook, a powerful tool in React for handling state changes and keeping your components reactive.

2. What is useState Hook?

useState Hook is a React function that lets you manage state within functional components. It's an alternative to using class-based components for state management.

3. Why useState Hook?

Why useState Hook?

useState Hook offers several benefits over class-based state management:

  • Simplicity: useState Hook is much simpler and easier to use compared to class-based state management.
  • Code Reusability: It promotes code reusability and maintainability, as state logic is isolated within functional components.
  • Performance: useState Hook can improve performance by avoiding unnecessary re-renders, especially in large applications.

4. useState Hook Syntax

useState Hook Syntax:

const [state, setState] = useState(initialState);

state is the current state value, and setState is a function that updates the state. initialState is the initial value of the state.

5. useState Hook Example Usage

Example Usage:

const [count, setCount] = useState(0);

const handleClick = () => {
  setCount(count + 1);
};

This code creates a state variable count with an initial value of 0. When the button is clicked, handleClick is called, which updates the count state using setCount.

6. useState Hook - State Update Methods

State Update Methods:

  • setState(updaterFunction): Updates the state based on the return value of the function provided.
  • setState(prevState => ()): Updates the state based on the previous state, useful for updating based on current state.

Note: State updates are asynchronous, and multiple updates may be batched together.

7. useEffect Hook - Intro

useEffect Hook - Introduction

useEffect Hook allows you to perform side effects in functional components, such as interacting with the DOM, fetching data, or setting up timers.

8. useEffect Hook - Dependency Array

useEffect Hook - Dependency Array

useEffect Hook accepts an optional second argument, a dependency array. When the values in the dependency array change, useEffect will re-run.

useEffect(() => {
  // Side-effect code
}, [dependencyArray]);

9. useEffect Hook - Cleanup Function

useEffect Hook - Cleanup Function

useEffect Hook can also return a cleanup function. This function is called when the component is unmounted or when the dependency array changes.

useEffect(() => {
  // Side-effect code

  return () => {
    // Cleanup function
  };
}, [dependencyArray]);

10. useEffect Hook - Common Use Cases

useEffect Hook - Common Use Cases

  • Fetching data from an API
  • Setting up event listeners
  • Creating timers or intervals
  • Performing cleanup actions

11. useEffect Hook - Best Practices

useEffect Hook - Best Practices

  • Keep dependency arrays as concise as possible.
  • Avoid using side effects inside render.
  • Use a cleanup function when necessary to prevent memory leaks.

12. Next Up: useContext Hook

In the next session, we'll explore the useContext Hook, a powerful tool for managing state across multiple components without prop drilling.

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