Question 1

How do I handle errors in async/await JavaScript functions?

Accepted Answer

Wrap await calls in try/catch blocks and check response.ok before parsing fetch results. For repeated failures, implement retry logic with exponential backoff, and use custom error classes like ApiError to carry status codes and response data.

Question 2

What is the difference between ESM and CommonJS modules in Node.js?

Accepted Answer

ESM uses import/export syntax with asynchronous loading, top-level await, and tree shaking support, while CommonJS uses require()/module.exports with synchronous loading. Set "type": "module" in package.json for ESM, and never mix both systems in the same module.

Question 3

How do I cancel a fetch request in JavaScript?

Accepted Answer

Use AbortController by creating a controller, passing its signal to fetch, and calling controller.abort() to cancel. The fetch promise rejects with an AbortError, which you can detect by checking error.name === 'AbortError' in the catch block.

Question 4

Does Promise.all fail if one promise rejects?

Accepted Answer

Yes, Promise.all rejects immediately when any promise rejects, discarding other results. Use Promise.allSettled to wait for all promises regardless of outcome, or Promise.any to resolve with the first successful result.

Question 5

When should I use Web Workers instead of the main thread?

Accepted Answer

Use Web Workers for CPU-intensive tasks like processing large arrays or complex calculations that would block the browser's main thread and freeze the UI. Communicate with workers via postMessage and onmessage, and terminate them when work completes.

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