npm package: @stdlib/streams-node-from-iterator
Description: Create a readable stream from an iterator.
Author: The Stdlib Authors
Latest version: 0.2.3

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# Iterator Stream

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Create a [readable stream][readable-stream] from an [iterator][mdn-iterator-protocol].

<section class="installation">

## Installation

```bash
npm install @stdlib/streams-node-from-iterator
```

</section>

<section class="usage">

## Usage

```javascript
var iteratorStream = require( '@stdlib/streams-node-from-iterator' );
```

<a name="iterator-stream"></a>

#### iteratorStream( iterator\[, options] )

Returns a [readable stream][readable-stream] from an [iterator][mdn-iterator-protocol].

```javascript
var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
var randu = require( '@stdlib/random-iter-randu' );

var iStream;
var stream;

function log( chunk, idx ) {
    console.log( chunk.toString() );
    if ( idx === 10 ) {
        stream.destroy();
    }
}

stream = iteratorStream( randu() );
iStream = inspectStream( log );

stream.pipe( iStream );
```

The function accepts the following `options`:

-   **objectMode**: specifies whether a [stream][stream] should operate in [objectMode][object-mode]. Default: `false`.
-   **encoding**: specifies how `Buffer` objects should be decoded to `strings`. Default: `null`.
-   **highWaterMark**: specifies the maximum number of bytes to store in an internal buffer before pausing iteration.
-   **sep**: separator used to join streamed data. This option is only applicable when a stream is **not** in [objectMode][object-mode]. Default: `'\n'`.
-   **serialize**: custom serialization function. This option is only applicable when a stream is **not** in [objectMode][object-mode].

To set [stream][stream] `options`,

```javascript
var randu = require( '@stdlib/random-iter-randu' );

var opts = {
    'objectMode': true,
    'encoding': 'utf8',
    'highWaterMark': 64
};

var stream = iteratorStream( randu(), opts );
```

By default, when not operating in [objectMode][object-mode], a returned [stream][stream] delineates iterated values using a newline character. To specify an alternative separator, set the `sep` option.

```javascript
var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
var randu = require( '@stdlib/random-iter-randu' );

function log( chunk ) {
    console.log( chunk.toString() );
}

var it = randu({
    'iter': 10
});

var stream = iteratorStream( it, {
    'sep': ','
});

var iStream = inspectStream( log );

stream.pipe( iStream );
```

By default, when not operating in [objectMode][object-mode], a returned [stream][stream] serializes iterated values as JSON strings. To specify custom serialization behavior (either to a `string` or `Buffer`), set the `serialize` option.

```javascript
var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
var randu = require( '@stdlib/random-iter-randu' );

function serialize( v ) {
    return 'r::' + v.toString();
}

function log( chunk ) {
    console.log( chunk.toString() );
}

var it = randu({
    'iter': 10
});

var stream = iteratorStream( it, {
    'serialize': serialize
});

var iStream = inspectStream( log );

stream.pipe( iStream );
```

* * *

#### iteratorStream.factory( \[options] )

Returns a `function` for creating [readable streams][readable-stream] from [iterators][mdn-iterator-protocol].

```javascript
var randu = require( '@stdlib/random-iter-randu' );

var opts = {
    'objectMode': true,
    'encoding': 'utf8',
    'highWaterMark': 64
};

var createStream = iteratorStream.factory( opts );

var stream1 = createStream( randu() );
var stream2 = createStream( randu() );
// ...
```

The method accepts the same `options` as [`iteratorStream()`](#iterator-stream).

* * *

#### iteratorStream.objectMode( iterator\[, options] )

This method is a convenience function to create [streams][stream] which **always** operate in [objectMode][object-mode].

```javascript
var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
var randu = require( '@stdlib/random-iter-randu' );

function log( v ) {
    console.log( v );
}

var opts = {
    'iter': 10
};
var stream = iteratorStream.objectMode( randu( opts ) );

opts = {
    'objectMode': true
};
var iStream = inspectStream( opts, log );

stream.pipe( iStream );
```

This method accepts the same `options` as [`iteratorStream()`](#iterator-stream); however, the method will **always** override the [`objectMode`][object-mode] option in `options`.

</section>

<!-- /.usage -->

* * *

<section class="notes">

## Notes

-   In [`objectMode`][object-mode], `null` is a reserved value. If an [iterator][mdn-iterator-protocol] generates `null` values (e.g., as a means to encode missing values), the stream will prematurely end. Consider an alternative encoding or explicitly map `null` values to a different value by wrapping the provided [iterator][mdn-iterator-protocol] with another [iterator][mdn-iterator-protocol].
-   In binary mode, if an [iterator][mdn-iterator-protocol] generates `undefined` values, the stream will emit an error. Consider providing a custom serialization function or explicitly map `undefined` values to a different value by wrapping the provided [iterator][mdn-iterator-protocol] with another [iterator][mdn-iterator-protocol].

</section>

<!-- /.notes -->

* * *

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
var randu = require( '@stdlib/random-iter-randu' );
var iteratorStream = require( '@stdlib/streams-node-from-iterator' );

function log( v ) {
    console.log( v.toString() );
}

// Create an iterator which generates uniformly distributed pseudorandom numbers:
var opts = {
    'iter': 10
};
var it = randu( opts );

// Convert the iterator to a stream:
opts = {
    'objectMode': true
};
var stream = iteratorStream( it, opts );

// Create a writable stream for inspecting stream data:
opts = {
    'objectMode': true
};
var iStream = inspectStream( opts, log );

// Begin data flow:
stream.pipe( iStream );
```

</section>

<!-- /.examples -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/streams-node/from-array`][@stdlib/streams/node/from-array]</span><span class="delimiter">: </span><span class="description">create a readable stream from an array-like object.</span>

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->


<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

#### Community

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

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[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules

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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/streams-node-from-iterator/main/LICENSE

[stream]: https://nodejs.org/api/stream.html

[object-mode]: https://nodejs.org/api/stream.html#stream_object_mode

[readable-stream]: https://nodejs.org/api/stream.html

[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol

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[@stdlib/streams/node/from-array]: https://www.npmjs.com/package/@stdlib/streams-node-from-array

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