What is the difference between sequential and parallel await in JavaScript?
Sequential await waits for each operation to complete before starting the next (total time is the sum). Parallel await with Promise.all starts all operations at once (total time is the longest operation). Use parallel for independent operations.
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More FAQs in Sequential vs Parallel await in JavaScript
When operations depend on each other. For example, const user = await fetchUser(id); const posts = await fetchPosts(user.id);. fetchPosts needs user.id, so you must wait for fetchUser first.
Use Promise.all: const [a, b, c] = await Promise.all([fetchA(), fetchB(), fetchC()]). Start all promises at once, then await all. This is much faster than sequential await for independent operations.
For independent items, use Promise.all with map: const results = await Promise.all(urls.map(url => fetch(url))). For dependent items, use sequential await in a for...of loop.
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