Redux ist ein praedizierbarer Zustandsbehaelter fuer JavaScript-Anwendungen, basierend auf dem unidirektionalen Datenfluss.
Kernkonzepte und Store-Erstellung
import { createStore } from 'redux';
// Reducer-Funktion: reine Funktion zur Berechnung des naechsten Zustands
function counterReducer(state = { value: 0 }, action) {
switch (action.type) {
case 'counter/incremented':
return { value: state.value + 1 };
case 'counter/decremented':
return { value: state.value - 1 };
default:
return state;
}
}
// Store instanziieren
const store = createStore(counterReducer);
// Auf Zustandsaenderungen abonnieren
const unsubscribe = store.subscribe(() => {
console.log('Aktueller Zustand:', store.getState());
});
// Actions dispatchen
store.dispatch({ type: 'counter/incremented' }); // { value: 1 }
store.dispatch({ type: 'counter/decremented' }); // { value: 0 }
Action-Creator und Middleware
// Action Creator
const incrementBy = (amount) => ({
type: 'counter/incrementBy',
payload: amount
});
// Middleware-Muster (Logging, asynchrone Thunks)
const loggerMiddleware = (storeAPI) => (next) => (action) => {
console.log('Action wird ausgefuehrt:', action);
const result = next(action);
console.log('Naechster Zustand:', storeAPI.getState());
return result;
};
React Redux Hooks (useSelector und useDispatch)
import React from 'react';
import { useSelector, useDispatch } from 'react-redux';
export function Counter() {
const count = useSelector((state) => state.value);
const dispatch = useDispatch();
return (
<div>
<span>Count: {count}</span>
<button onClick={() => dispatch({ type: 'counter/incremented' })}>
+
</button>
</div>
);
}
Modernes Redux Toolkit (RTK)
Moderne Redux-Anwendungen setzen auf Redux Toolkit (createSlice, configureStore) zur Code-Reduktion:
import { createSlice, configureStore } from '@reduxjs/toolkit';
const counterSlice = createSlice({
name: 'counter',
initialState: { value: 0 },
reducers: {
increment: (state) => { state.value += 1; },
decrement: (state) => { state.value -= 1; }
}
});
export const { increment, decrement } = counterSlice.actions;
export const store = configureStore({ reducer: counterSlice.reducer });