Intermediate LevelReact JS & React 19
How does the new React 19 use() API unwrap Promises and Contexts conditionally?
❓ Interview Prompt: Explain React 19 `use(resource)` API, unwrapping Promises inside render, reading Context conditionally, and integration with Suspense.
React 19 introduces the 'use(resource)' API, a versatile function for unwrapping Promises and Contexts:
Key Differences from Standard Hooks:
1
Conditional Callability: 'use()' is the ONLY React API that can be called conditionally inside 'if' statements, 'for' loops, and early returns!
2
Promise Unwrapping: When passed a Promise ('use(promise)'), it suspends the component until the Promise resolves, integrating directly with '<Suspense>'.
Code Implementation Example
jsx
import { use, Suspense } from 'react';
function UserDetails({ userPromise, showDetails }) {
// 1. Conditional Context reading (Impossible with useContext!)
if (!showDetails) return <p>Details hidden</p>;
const theme = use(ThemeContext);
// 2. Promise Unwrapping (Suspends until userPromise resolves!)
const user = use(userPromise);
return <div className={theme}>{user.name}</div>;
}💡Conditionally reading Context and unwrapping Promises using React 19 use() API.
🎯 Interview Key Takeaway
React 19's use() API can be called inside conditional statements and loops to unwrap Promises and Context values.
#React 19#use()#Suspense#Promises#Intermediate
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