What is Redux?

Learn the Redux state management framework.

What is Redux?

Redux is a state management framework that keeps all of the app's state in a single object (the store). It centralizes shared data between components and reduces prop drilling. It has three core parts: store (state), action (change request) and reducer (pure function that applies the change).

The flow is one-directional: a component calls dispatch(action), the reducer returns the new state based on the action, the store updates, and the component reads the new state. This flow makes things predictable and debugging easier. Redux is common in large React Native apps.

Action and reducer

An action is an object describing what to do: { type: 'counter/increment' }. type is required; it may also carry a payload. A reducer takes the current state and an action and returns a new state. Important: the reducer must be pure; the same input always gives the same output and there are no side effects.

Example reducer: function counter(state = 0, action) { if (action.type === 'counter/increment') return state + 1; return state; }. State is never mutated directly; a new object is always returned. This rule is the basis of Redux's predictability.

Exercise Write the action object

Define incrementAction. It should be { type: 'counter/increment' }. Export it with export const.

Show example solution

export const incrementAction = { type: 'counter/increment' };

Test yourself

Where is state kept in Redux?
- In a single store
- Inside each component
- Only in AsyncStorage
- Only in the file system
Show answer

In a single store — Redux keeps all state in a single store.

Write the action type

{ type: '____/increment' }

Show answer

{ type: 'counter/increment' }

Match each part to its role

store

Holds the state
action

Change request
reducer

Returns new state
dispatch

Sends the action

Next lesson: Redux Toolkit

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