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doc: remove redunant await calls from stream docs
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PR-URL: #41592
Reviewed-By: Benjamin Gruenbaum <[email protected]>
Reviewed-By: Nitzan Uziely <[email protected]>
Reviewed-By: Mestery <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
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gioragutt authored and danielleadams committed Mar 3, 2022
1 parent 8758403 commit 1db96c8
Showing 1 changed file with 61 additions and 2 deletions.
63 changes: 61 additions & 2 deletions doc/api/stream.md
Original file line number Diff line number Diff line change
Expand Up @@ -1716,7 +1716,7 @@ for await (const item of Readable.from([1, 2, 3, 4]).map((x) => x * 2)) {
}
// With an asynchronous mapper, making at most 2 queries at a time.
const resolver = new Resolver();
const dnsResults = await Readable.from([
const dnsResults = Readable.from([
'nodejs.org',
'openjsf.org',
'www.linuxfoundation.org',
Expand Down Expand Up @@ -1761,7 +1761,7 @@ for await (const item of Readable.from([1, 2, 3, 4]).filter((x) => x > 2)) {
}
// With an asynchronous predicate, making at most 2 queries at a time.
const resolver = new Resolver();
const dnsResults = await Readable.from([
const dnsResults = Readable.from([
'nodejs.org',
'openjsf.org',
'www.linuxfoundation.org',
Expand All @@ -1775,6 +1775,65 @@ for await (const result of dnsResults) {
}
```

### `readable.forEach(fn[, options])`

<!-- YAML
added: REPLACEME
-->

> Stability: 1 - Experimental
* `fn` {Function|AsyncFunction} a function to call on each item of the stream.
* `data` {any} a chunk of data from the stream.
* `options` {Object}
* `signal` {AbortSignal} aborted if the stream is destroyed allowing to
abort the `fn` call early.
* `options` {Object}
* `concurrency` {number} the maximum concurrent invocation of `fn` to call
on the stream at once. **Default:** `1`.
* `signal` {AbortSignal} allows destroying the stream if the signal is
aborted.
* Returns: {Promise} a promise for when the stream has finished.

This method allows iterating a stream. For each item in the stream the
`fn` function will be called. If the `fn` function returns a promise - that
promise will be `await`ed.

This method is different from `for await...of` loops in that it can optionally
process items concurrently. In addition, a `forEach` iteration can only be
stopped by having passed a `signal` option and aborting the related
`AbortController` while `for await...of` can be stopped with `break` or
`return`. In either case the stream will be destroyed.

This method is different from listening to the [`'data'`][] event in that it
uses the [`readable`][] event in the underlying machinary and can limit the
number of concurrent `fn` calls.

```mjs
import { Readable } from 'stream';
import { Resolver } from 'dns/promises';

// With a synchronous predicate.
for await (const item of Readable.from([1, 2, 3, 4]).filter((x) => x > 2)) {
console.log(item); // 3, 4
}
// With an asynchronous predicate, making at most 2 queries at a time.
const resolver = new Resolver();
const dnsResults = Readable.from([
'nodejs.org',
'openjsf.org',
'www.linuxfoundation.org',
]).map(async (domain) => {
const { address } = await resolver.resolve4(domain, { ttl: true });
return address;
}, { concurrency: 2 });
await dnsResults.forEach((result) => {
// Logs result, similar to `for await (const result of dnsResults)`
console.log(result);
});
console.log('done'); // Stream has finished
```

### Duplex and transform streams

#### Class: `stream.Duplex`
Expand Down

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