Local vs Global State

When managing state in a React application, you have the option to store state either locally within a component or globally using a state management solution. Both approaches have their own advantages and considerations.

Local Component State

Local component state refers to state that is stored and managed within a specific component. The state is only accessible and modifiable by the component and its child components.

Local state is useful for managing data that is specific to a single component or does not need to be shared across multiple components. It provides encapsulation and separation of concerns, as each component can maintain its own state independently.

Here's an example of local state in a React component:

1import React, { useState } from 'react';
2
3function Counter() {
4  const [count, setCount] = useState(0);
5
6  const increment = () => {
7    setCount(count + 1);
8  };
9
10  return (
11    <div>
12      <p>Count: {count}</p>
13      <button onClick={increment}>Increment</button>
14    </div>
15  );
16}
17
18export default Counter;

In this example, the count state is local to the Counter component. The component renders the current count value and provides a button to increment the count.

Global State Management

Global state management solutions, such as Redux or MobX, allow you to store and manage state that can be accessed by any component in your application. Global state provides a centralized store where multiple components can read and update shared data.

Global state management is useful for scenarios where components need to share data or communicate with each other. It helps avoid prop drilling, where data needs to be passed down through multiple layers of components that don't directly use the data.

Here's an example of using Redux to manage global state:

1import { createStore } from 'redux';
2
3// Define an initial state
4const initialState = {
5  count: 0,
6};
7
8// Define a reducer
9const reducer = (state = initialState, action) => {
10  switch (action.type) {
11    case 'INCREMENT':
12      return {
13        ...state,
14        count: state.count + 1,
15      };
16    case 'DECREMENT':
17      return {
18        ...state,
19        count: state.count - 1,
20      };
21    default:
22      return state;
23  }
24};
25
26// Create a Redux store
27const store = createStore(reducer);
28
29// Access the global state
30console.log(store.getState().count);

In this example, the count state is stored globally using Redux. Any component in the application can access the count value using the store.

When deciding between local or global state, consider the complexity and size of your application. Local state is useful for simple and self-contained components, while global state management solutions are suitable for larger applications or when multiple components need to share data.