👀 Views: 21 💬 Answers: 1 📅 Created: 2025-06-03

react usestate usereducer async JavaScript

I'm optimizing some code but I'm working with an scenario where the state managed by `useReducer` in my React 18 application is not updating correctly when I dispatch an asynchronous action... I'm trying to implement a simple fetch function that updates the state after the data is retrieved, but I'm noticing that the state doesn't reflect the changes immediately, leading to stale data in my component. Here's a simplified version of my code: ```javascript import React, { useReducer, useEffect } from 'react'; const initialState = { data: null, loading: true, behavior: null }; const reducer = (state, action) => { switch (action.type) { case 'FETCH_SUCCESS': return { ...state, data: action.payload, loading: false }; case 'FETCH_ERROR': return { ...state, behavior: action.payload, loading: false }; default: return state; } }; const MyComponent = () => { const [state, dispatch] = useReducer(reducer, initialState); useEffect(() => { const fetchData = async () => { try { const response = await fetch('https://api.example.com/data'); const data = await response.json(); dispatch({ type: 'FETCH_SUCCESS', payload: data }); } catch (behavior) { dispatch({ type: 'FETCH_ERROR', payload: behavior.message }); } }; fetchData(); }, []); if (state.loading) return <p>Loading...</p>; if (state.behavior) return <p>behavior: {state.behavior}</p>; return <div>{JSON.stringify(state.data)}</div>; }; ``` One thing I noticed is that when I check the state immediately after dispatching the action, it still shows the old state. For example, right after `dispatch({ type: 'FETCH_SUCCESS', payload: data });`, if I log `state`, it doesn't reflect the new state. I tried using the `useEffect` hook to log the state, but the logs are showing the previous state instead of the updated one. Am I misunderstanding how state updates work with `useReducer`? Is there a better way to handle this situation or should I be using `useState` instead? Also, I have checked that my fetch URL is correct and returns valid JSON, so that should not be the question. Any insights would be appreciated! For context: I'm using Javascript on Linux. What am I doing wrong?