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devexamples

Async Generator Batched Iteration

Pull remote pages lazily through an async generator, batching records per yield so consumers control pacing and memory stays flat.

JavascriptData Fetching

Code

snippet
async function* paginate(source, pageSize = 100) {
  let offset = 0;
  while (true) {
    const rows = await source(offset, pageSize);
    if (rows.length === 0) return;
    yield rows;
    offset += rows.length;
  }
}

async function* flatten(batches) {
  for await (const batch of batches) {
    for (const row of batch) {
      yield row;
    }
  }
}

const remote = async (offset, limit) => {
  const res = await fetch(
    'https://api.example.com/records?offset=' + offset + '&limit=' + limit,
  );
  const body = await res.json();
  return body.rows;
};

let total = 0;
for await (const row of flatten(paginate(remote))) {
  total += row.amount;
  if (total > 10_000) break; // 消费者随时可提前退出
}
console.log('accumulated amount:', total);

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