javascript Questions
1 months ago
How to write effective unit tests for React components with Vitest?
I'm setting up testing for my React app using Vitest + React Testing Library. I'm not sure about best practices:
- Should I test implementation details (internal state) or only behavior?
- How do I test components that make API calls?
- When should I use
vi.mock()?
Looking for practical examples, not just "test behavior not implementation."
L
Lena Müller
asked 1 months ago
1
Answers
114
Upvotes
4100
Views2 months ago
React: useEffect dependency array — when does it cause infinite loops?
My component keeps re-rendering infinitely. Here's a simplified version:
function MyComponent({ onUpdate }) {
const [data, setData] = useState(null);
useEffect(() => {
fetchSomething().then(setData);
onUpdate(data);
}, [onUpdate, data]);
}I think the issue is with onUpdate but I'm not sure. What are the rules for the dependency array?
2 months ago
How do I handle async/await errors properly in JavaScript?
I've been using async/await in my Node.js app but I keep running into unhandled promise rejections. Here's my current code:
async function fetchData() {
const res = await fetch('https://api.example.com/data');
const json = await res.json();
return json;
}What's the correct pattern for catching errors? Should I use try/catch everywhere or is there a better approach?
4 months ago
JWT authentication — where should I store the token?
I'm implementing JWT-based auth in a Next.js app. I've read conflicting advice about where to store the JWT:
- localStorage: easy but vulnerable to XSS
- httpOnly cookies: XSS-safe but CSRF risk
- Memory (JS variable): safest but lost on refresh
What's the recommended approach in 2024 for a production app? Does it change if I'm using NextAuth?