How do you batch process with concurrency limits using promises in JavaScript?
Process batchSize items at a time with Promise.all: for (let i = 0; i < items.length; i += batchSize) { await Promise.all(items.slice(i, i + batchSize).map(processFn)); }. This avoids overwhelming the server.
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More FAQs in Promise Combinators: Real-World Examples in JavaScript
Loading multiple resources in parallel (user, posts, friends), fetching multiple pages, parallel data transformation, and batch processing with limits. Any scenario where you need all results and any failure is a total failure.
Best-effort data fetching (dashboard widgets that may fail individually), partial success scenarios, and when you want all results regardless of failures. Some widgets fail, but the page still loads with available data.
Timeouts (race an operation against a timeout promise), first successful source (whichever responds first), and cancellation patterns. Common for API calls that should not hang forever.
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