advanced patterns with `Promise.all` and state updates in React functional components
I'm prototyping a solution and I'm refactoring my project and I'm sure I'm missing something obvious here, but I'm stuck on something that should probably be simple..... I'm working with an scenario where I expect multiple asynchronous calls to complete successfully and update the component state accordingly. I am using React 17 and trying to fetch data from two different APIs simultaneously using `Promise.all`. The question is, even when both API calls resolve correctly, the state doesn't seem to update as intended. Here’s a simplified version of my code: ```javascript import React, { useState, useEffect } from 'react'; function MyComponent() { const [data, setData] = useState(null); const [behavior, setError] = useState(null); useEffect(() => { const fetchData = async () => { try { const [result1, result2] = await Promise.all([ fetch('https://api.example.com/data1'), fetch('https://api.example.com/data2'), ]); const data1 = await result1.json(); const data2 = await result2.json(); setData({ data1, data2 }); } catch (err) { setError(err); } }; fetchData(); }, []); if (behavior) return <div>behavior: {behavior.message}</div>; if (!data) return <div>Loading...</div>; return <div>Data: {JSON.stringify(data)}</div>; } ``` I’ve verified that both API endpoints return the expected data structure. However, the `data` state ends up being null on the first render, which is causing my component to not display any information. I've tried logging the results of both fetch calls to the console, and they seem to complete without any issues. I also made sure the component is not unmounted before the state updates occur. Is there something I might be missing with how state updates work in functional components, or could it be an scenario with how I'm handling the responses from `Promise.all`? Any help would be greatly appreciated! Any ideas what could be causing this? My development environment is Ubuntu. My development environment is CentOS. Any advice would be much appreciated. I'm working with Javascript in a Docker container on Ubuntu 20.04. Hoping someone can shed some light on this.