Async Iteration and Backpressure with for await...of

Wed, 02 Sep 2026 00:00:00 +0700

JavaScript promises represent one future result. Many systems produce a sequence of future results instead: paginated records, stream chunks, queue messages, or events from an asynchronous source.

Async iteration models that shape directly. An async iterable exposes values over time, and for await...of consumes them one at a time.

A minimal async generator

An async generator can yield values after asynchronous work:

copied = false, 1600)" class="absolute right-3 top-3 z-10 rounded-lg border border-line-strong bg-surface px-2 py-1 font-mono text-[0.65rem] text-muted opacity-0 transition group-hover:opacity-100 hover:bg-ink hover:text-white dark:border-night-line dark:bg-night dark:text-night-muted dark:hover:bg-white dark:hover:text-ink">

async function* pages() {
  for (let page = 1; page <= 3; page++) {
    const response = await fetch(`https://example.com/api/items?page=${page}`);

    if (!response.ok) {
      throw new Error(`HTTP ${response.status}`);
    }

    yield await response.json();
  }
}

for await (const page of pages()) {
  console.log(page);
}

The consumer does not need to know how pagination is implemented. It only sees an asynchronous sequence.

Reading Streams Correctly in Go with io.Reader

Wed, 02 Sep 2026 00:00:00 +0700

Go’s io.Reader interface is tiny:

type Reader interface {
    Read(p []byte) (n int, err error)
}

Its small surface hides an important contract: a read is allowed to return fewer bytes than the buffer can hold, and it can return useful bytes together with an error. Correct stream processing must handle both cases.

Streams on Nalar

Async Iteration and Backpressure with for await...of

A minimal async generator

Reading Streams Correctly in Go with io.Reader