npm package: @stdlib/streams-node-inspect-sink
Description: Writable stream for inspecting streamed data.
Author: The Stdlib Authors
Latest version: 0.2.3

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</details>

# Inspect Stream

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

> [Writable stream][writable-stream] for inspecting streamed data.

<section class="installation">

## Installation

```bash
npm install @stdlib/streams-node-inspect-sink
```

</section>

<section class="usage">

## Usage

```javascript
var inspectSinkStream = require( '@stdlib/streams-node-inspect-sink' );
```

<a name="inspect-sink-stream"></a>

#### inspectSinkStream( \[options,] clbk )

Creates a [writable stream][writable-stream] for inspecting streamed data.

```javascript
function log( chunk, idx ) {
    console.log( 'index: %d', idx );
    console.log( chunk );
}

var stream = inspectSinkStream( log );

stream.write( 'a' );
stream.write( 'b' );
stream.write( 'c' );

stream.end();

// prints: index: 0
// prints: a
// prints: index: 1
// prints: b
// prints: index: 2
// prints: c
```

The function accepts the following `options`:

-   **objectMode**: specifies whether a [stream][stream] should operate in [objectMode][object-mode]. Default: `false`.
-   **highWaterMark**: specifies the `Buffer` level at which `write()` calls start returning `false`.
-   **decodeStrings**: specifies whether to encode strings as `Buffer` objects before writing data to a returned [stream][stream]. Default: `true`.
-   **defaultEncoding**: default encoding when not explicitly specified when writing data. Default: `'utf8'`.

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

```javascript
function log( chunk, idx ) {
    console.log( 'index: %d', idx );
    console.log( chunk );
}

var opts = {
    'objectMode': true,
    'highWaterMark': 64,
    'decodeStrings': false,
    'defaultEncoding': 'utf8'
};

var stream = inspectSinkStream( opts, log );
```

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

Returns a `function` for creating [streams][writable-stream] which are identically configured according to provided `options`.

```javascript
var opts = {
    'objectMode': true,
    'highWaterMark': 64
};

var factory = inspectSinkStream.factory( opts );
```

This method accepts the same `options` as [`inspectSinkStream()`](#inspect-sink-stream).

##### factory( clbk )

Creates a [writable stream][writable-stream] for inspecting streamed data.

```javascript
function log( chunk, idx ) {
    console.log( 'index: %d', idx );
    console.log( chunk );
}

var factory = inspectSinkStream.factory();

// Create 10 identically configured streams...
var streams = [];
var i;
for ( i = 0; i < 10; i++ ) {
    streams.push( factory( log ) );
}
```

#### inspectSinkStream.objectMode( \[options,] clbk )

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

<!-- eslint-disable object-curly-newline -->

```javascript
function log( chunk, idx ) {
    console.log( 'index: %d', idx );
    console.log( chunk );
}

var stream = inspectSinkStream.objectMode( log );

stream.write( { 'value': 'a' } );
stream.write( { 'value': 'b' } );
stream.write( { 'value': 'c' } );

stream.end();

// prints: index: 0
// prints: {'value': 'a'}
// prints: index: 1
// prints: {'value': 'b'}
// prints: index: 2
// prints: {'value': 'c'}
```

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

</section>

<!-- /.usage -->

<section class="examples">

## Examples

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

```javascript
var parseJSON = require( '@stdlib/utils-parse-json' );
var transformFactory = require( '@stdlib/streams-node-transform' ).factory;
var inspect = require( '@stdlib/streams-node-inspect-sink' ).objectMode;

function parse( chunk, enc, clbk ) {
    clbk( null, parseJSON( chunk ) );
}

function pluck( chunk, enc, clbk ) {
    clbk( null, chunk.value );
}

function square( chunk, enc, clbk ) {
    var v = +chunk;
    clbk( null, v*v );
}

function toStr( chunk, enc, clbk ) {
    clbk( null, chunk.toString() );
}

function join( chunk, enc, clbk ) {
    clbk( null, chunk+'\n' );
}

function logger( chunk, idx ) {
    console.log( 'index: %d', idx );
    console.log( chunk );
}

// Create a factory for generating streams running in `objectMode`:
var tStream = transformFactory({
    'objectMode': true
});

// Create streams for each transform:
var s1 = tStream( parse );
var s2 = tStream( pluck );
var s3 = tStream( square );
var s4 = tStream( toStr );
var s5 = tStream( join );

// Create a writable stream for inspecting the result of the transformations:
var is = inspect( logger );

// Create the pipeline:
s1.pipe( s2 )
    .pipe( s3 )
    .pipe( s4 )
    .pipe( s5 )
    .pipe( is );

// Write data to the pipeline...
var v;
var i;
for ( i = 0; i < 100; i++ ) {
    v = '{"value":'+i+'}';
    s1.write( v, 'utf8' );
}
s1.end();
```

</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/debug-sink`][@stdlib/streams/node/debug-sink]</span><span class="delimiter">: </span><span class="description">writable stream for debugging stream pipelines.</span>
-   <span class="package-name">[`@stdlib/streams-node/inspect`][@stdlib/streams/node/inspect]</span><span class="delimiter">: </span><span class="description">transform stream for inspecting streamed data.</span>

</section>

<!-- /.related -->

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<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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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/streams-node-inspect-sink/main/LICENSE

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

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

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

<!-- <related-links> -->

[@stdlib/streams/node/debug-sink]: https://www.npmjs.com/package/@stdlib/streams-node-debug-sink

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

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</section>

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