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REFERENCEreact

react Documentation

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Redux

AI & DATA SCIENCE // redux

Redux is a standalone, predictable state-management library commonly used with React, storing all application state in a single centralized store updated only through dispatched actions.

Syntax

npm install redux react-redux

Deep Dive Course

Redux organizes application state around three core principles: a single store holding the entire application's state as one object tree, state that's only ever changed by dispatching a plain action object describing what happened, and pure reducer functions that take the current state and an action and return a new state, never mutating the original. Paired with the react-redux library, components can read from the store using the useSelector hook and dispatch actions using the useDispatch hook, keeping the actual Redux logic decoupled from any specific component.

1Understanding Redux

Redux organizes application state around three core principles: a single store holding the entire application's state as one object tree, state that's only ever changed by dispatching a plain action object describing what happened, and pure reducer functions that take the current state and an action and return a new state, never mutating the original. Paired with the react-redux library, components can read from the store using the useSelector hook and dispatch actions using the useDispatch hook, keeping the actual Redux logic decoupled from any specific component.

💡

Redux enforces a strict, predictable update pattern, every state change goes through a dispatched action and a pure reducer, which is exactly what enables powerful developer tools like time-travel debugging, at the cost of noticeably more boilerplate than simpler alternatives like plain Context for smaller applications.

editor.html
# Terminal
npm install redux react-redux @reduxjs/toolkit
localhost:3000

2Practical Example

Here is a real-world application of Redux showing how it is used in production React code.

editor.html
import { Provider } from 'react-redux';
import { store } from './store';

function App() {
  return (
    <Provider store={store}>
      <MyComponents />
    </Provider>
  );
}
localhost:3000

3Best Practices

Follow these guidelines when working with Redux:

1. Reach for Redux specifically when an application has substantial, frequently-updating shared state across many unrelated components, along with a real need for tooling like time-travel debugging

2. Keep reducers pure, computing a new state object based only on the current state and the action, with no side effects or mutations of the existing state

3. Use react-redux's useSelector and useDispatch hooks inside components to read from and update the store, rather than importing the store instance directly wherever needed

⚠️

Tip: Redux enforces a strict, predictable update pattern, every state change goes through a dispatched action and a pure reducer, which is exactly what enables powerful developer tools like time-travel debugging, at the cost of noticeably more boilerplate than simpler alternatives like plain Context for smaller applications.

editor.html
# Terminal
npm install redux react-redux @reduxjs/toolkit
localhost:3000

Examples

Example 01Basic Usage
# Terminal
npm install redux react-redux @reduxjs/toolkit
Example 02Advanced Example
import { Provider } from 'react-redux';
import { store } from './store';

function App() {
  return (
    <Provider store={store}>
      <MyComponents />
    </Provider>
  );
}

Best Practices

  • Reach for Redux specifically when an application has substantial, frequently-updating shared state across many unrelated components, along with a real need for tooling like time-travel debugging
  • Keep reducers pure, computing a new state object based only on the current state and the action, with no side effects or mutations of the existing state
  • Use react-redux's useSelector and useDispatch hooks inside components to read from and update the store, rather than importing the store instance directly wherever needed

Interview Question

Why does Redux require state updates to go strictly through dispatched actions and pure reducer functions, rather than allowing components to directly mutate the store's state?

Hint: Think about what predictability and tooling benefits, like time-travel debugging, actually depend on every state change being expressed the same structured way.

Requiring every state change to be expressed as a plain, serializable action object processed by a pure reducer function means every single update to the application's state follows one single, structured, traceable pattern, rather than state potentially being mutated ad hoc from anywhere in the codebase in whatever way a particular component happens to choose. This structured discipline is exactly what enables Redux's most powerful developer tools: since every state transition is just old state plus a specific action producing new state, with reducers being pure functions with no hidden side effects, tools like Redux DevTools can record the complete, ordered sequence of every dispatched action, replay them to reconstruct any past state, and even let a developer travel backward and forward through that history, called time-travel debugging. None of that would be reliably possible if components could mutate the store's state directly and arbitrarily, since there would be no consistent, structured record of what changed, when, or why.

Exercises

MediumPractice using Redux in a real scenario.
View Solution
# Terminal
npm install redux react-redux @reduxjs/toolkit

Frequently Asked Questions

Why does Redux require state updates to go strictly through dispatched actions and pure reducer functions, rather than allowing components to directly mutate the store's state?

Requiring every state change to be expressed as a plain, serializable action object processed by a pure reducer function means every single update to the application's state follows one single, structured, traceable pattern, rather than state potentially being mutated ad hoc from anywhere in the codebase in whatever way a particular component happens to choose. This structured discipline is exactly what enables Redux's most powerful developer tools: since every state transition is just old state plus a specific action producing new state, with reducers being pure functions with no hidden side effects, tools like Redux DevTools can record the complete, ordered sequence of every dispatched action, replay them to reconstruct any past state, and even let a developer travel backward and forward through that history, called time-travel debugging. None of that would be reliably possible if components could mutate the store's state directly and arbitrarily, since there would be no consistent, structured record of what changed, when, or why.

Related Functions

storereducersactions