Inspect Stream

Writable stream for inspecting streamed data.

Usage

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

inspectSinkStream( [options,] clbk )

Creates a writable stream for inspecting streamed data.

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 should operate in objectMode. 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. Default: true.
defaultEncoding: default encoding when not explicitly specified when writing data. Default: 'utf8'.

To set stream options,

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 which are identically configured according to provided options.

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

var factory = inspectSinkStream.factory( opts );

This method accepts the same options as inspectSinkStream().

factory( clbk )

Creates a writable stream for inspecting streamed data.

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 which always operate in objectMode.

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(); however, the method will always override the objectMode option in options.

Examples

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();