40. Async iterators and for-await-of

Async generators produce values over time, and `for await...of` consumes them one at a time, awaiting each. Readable streams are themselves async iterable, which is often cleaner than juggling `"data"`/`"end"` event listeners.

js
async function* paginate(fetchPage) {
  let page = 1;
  while (true) {
    const items = await fetchPage(page++);
    if (items.length === 0) return;
    yield* items;
  }
}

for await (const item of paginate(fetchTransactionsPage)) {
  console.log(item.hash);
}

// a Readable stream is also async-iterable:
for await (const chunk of createReadStream("./data.csv")) {
  process(chunk);
}

This pattern shines for paginated blockchain indexer APIs, where you want to process an unbounded sequence of results without loading them all into memory up front.

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