JavaScriptawait tuần tự từng operation sẽ chậm hơn.
Chạy song song bằng cách tạo tất cả Promises trước rồi mới await.
javascript
// Sequential — chậm (mỗi request phải chờ cái trước)
const user = await fetchUser(id);
const posts = await fetchPosts(id); // chờ user xong mới gọi
// Parallel — nhanh hơn
const [user, posts] = await Promise.all([
fetchUser(id),
fetchPosts(id),
]);
// Tránh await trong loop (serial)
for (const id of ids) {
await fetchItem(id); // BAD: 1 by 1
}
// Dùng Promise.all cho parallel
const items = await Promise.all(ids.map(id => fetchItem(id)));Sequentially awaiting each operation is slower.
Run in parallel by creating all Promises first, then awaiting them.
javascript
// Sequential — slow (each request waits for the previous)
const user = await fetchUser(id);
const posts = await fetchPosts(id); // waits for user first
// Parallel — much faster
const [user, posts] = await Promise.all([
fetchUser(id),
fetchPosts(id),
]);
// Avoid await inside loops (serial)
for (const id of ids) {
await fetchItem(id); // BAD: 1 by 1
}
// Use Promise.all for parallel
const items = await Promise.all(ids.map(id => fetchItem(id)));