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https://github.com/stdlib-js/streams-node-from-iterator

Create a readable stream from an iterator.
https://github.com/stdlib-js/streams-node-from-iterator

convert iter iterate iterator javascript node node-js nodejs readable stdlib stream streams to util utilities utility utils

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Create a readable stream from an iterator.

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README 

        



  

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# Iterator Stream



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



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



## Installation



```bash

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

```



Alternatively,



-   To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).

-   If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).

-   For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).



The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.



To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.



## Usage



```javascript

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

```






#### 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`.



* * *



## 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].



* * *



## Examples



```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 );

```



* * *



## See Also



-   [`@stdlib/streams-node/from-array`][@stdlib/streams/node/from-array]: create a readable stream from an array-like object.



* * *



## 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 © 2016-2024. The Stdlib [Authors][stdlib-authors].



[npm-image]: http://img.shields.io/npm/v/@stdlib/streams-node-from-iterator.svg

[npm-url]: https://npmjs.org/package/@stdlib/streams-node-from-iterator



[test-image]: https://github.com/stdlib-js/streams-node-from-iterator/actions/workflows/test.yml/badge.svg?branch=main

[test-url]: https://github.com/stdlib-js/streams-node-from-iterator/actions/workflows/test.yml?query=branch:main



[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/streams-node-from-iterator/main.svg

[coverage-url]: https://codecov.io/github/stdlib-js/streams-node-from-iterator?branch=main



[chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg

[chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im



[stdlib]: https://github.com/stdlib-js/stdlib



[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors



[umd]: https://github.com/umdjs/umd

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



[deno-url]: https://github.com/stdlib-js/streams-node-from-iterator/tree/deno

[deno-readme]: https://github.com/stdlib-js/streams-node-from-iterator/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/streams-node-from-iterator/tree/umd

[umd-readme]: https://github.com/stdlib-js/streams-node-from-iterator/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/streams-node-from-iterator/tree/esm

[esm-readme]: https://github.com/stdlib-js/streams-node-from-iterator/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/streams-node-from-iterator/blob/main/branches.md



[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



[@stdlib/streams/node/from-array]: https://github.com/stdlib-js/streams-node-from-array