time-to-botec

README.md (5982B)

---

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 @license Apache-2.0
 
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 See the License for the specific language governing permissions and
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 # Debug Stream
 
 > [Transform stream][transform-stream] for [debugging][node-debug] stream pipelines.
 
 <section class="usage">
 
 ## Usage
 
 ```javascript
 var debugStream = require( '@stdlib/streams/node/debug' );
 ```
 
 <a name="debug-stream"></a>
 
 #### debugStream( \[options,] \[clbk] )
 
 Creates a [transform stream][transform-stream] for [debugging][node-debug] stream pipelines.
 
 ```javascript
 var ENV = require( '@stdlib/process/env' );
 
 // Set the `DEBUG` environment variable...
 ENV.DEBUG = '*';
 
 var stream = debugStream({
     'name': 'my-stream'
 });
 
 stream.write( 'a' );
 stream.write( 'b' );
 stream.write( 'c' );
 stream.end();
 ```
 
 The function accepts the following `options`:
 
 -   **name**: [debug][node-debug] namespace.
 -   **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`.
 -   **allowHalfOpen**: specifies whether a [stream][stream] should remain open even if one side ends. Default: `false`.
 -   **readableObjectMode**: specifies whether the readable side should be in [objectMode][object-mode]. Default: `false`.
 
 To set [stream][stream] `options`,
 
 ```javascript
 var opts = {
     'name': 'my-app',
     'objectMode': true,
     'highWaterMark': 64,
     'allowHalfOpen': true,
     'readableObjectMode': false // overridden by `objectMode` option when `objectMode=true`
 };
 
 var stream = debugStream( opts );
 ```
 
 By default, each `chunk` is logged as a JSON stringified `string`, along with the `chunk` index. For more control over logging behavior, provide a `callback`.
 
 ```javascript
 function logger( debug, chunk, idx ) {
     debug( 'Received a new chunk...' );
     debug( 'Beep: %s', chunk.beep );
     debug( 'Boop: %s', chunk.boop );
 }
 
 var opts = {
     'name': 'my-pipeline'
 };
 
 var stream = debugStream( opts, logger );
 ```
 
 #### debugStream.factory( \[options] )
 
 Returns a `function` for creating [streams][transform-stream] which are identically configured according to provided `options`.
 
 ```javascript
 var opts = {
     'objectMode': true,
     'highWaterMark': 64
 };
 
 var factory = debugStream.factory( opts );
 ```
 
 This method accepts the same `options` as [`debugStream()`](#debug-stream), **except** for `name`, which must be provided **explicitly**.
 
 ##### factory( name\[, clbk] )
 
 Creates a [debug][node-debug] stream.
 
 ```javascript
 var factory = debugStream.factory();
 
 var streams = [];
 var i;
 
 // Assign each stream to a separate debug namespace...
 for ( i = 0; i < 10; i++ ) {
     streams.push( factory( 'stream '+i ) );
 }
 ```
 
 #### debugStream.objectMode( \[options,] \[clbk] )
 
 This method is a convenience function to create [streams][stream] which **always** operate in [objectMode][object-mode].
 
 ```javascript
 var stream = debugStream.objectMode({
     'name': 'beep-boop'
 });
 
 stream.write({
     'value': 'a'
 });
 stream.write({
     'value': 'b'
 });
 stream.write({
     'value': 'c'
 });
 stream.end();
 ```
 
 This method accepts the same `options` as [`debugStream()`](#debug-stream); however, the method will **always** override the [objectMode][object-mode] option in `options`.
 
 </section>
 
 <!-- /.usage -->
 
 <section class="notes">
 
 ## Notes
 
 -   If the [`DEBUG`][node-debug] environment variable is **not** set, no data is logged.
 -   Providing a `name` option is **strongly** encouraged, as the [`DEBUG`][node-debug] environment variable can be used to filter debuggers.
 
 </section>
 
 <!-- /.notes -->
 
 <section class="examples">
 
 ## Examples
 
 <!-- eslint no-undef: "error" -->
 
 ```javascript
 var parseJSON = require( '@stdlib/utils/parse-json' );
 var stdout = require( '@stdlib/streams/node/stdout' );
 var transformFactory = require( '@stdlib/streams/node/transform' ).factory;
 var debug = require( '@stdlib/streams/node/debug' ).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' );
 }
 
 // Create a factory for generating streams running in `objectMode`:
 var tStream = transformFactory({
     'objectMode': true
 });
 
 // Create streams for each transform:
 var s1 = tStream( parse );
 var d1 = debug({
     'name': 'parse'
 });
 var s2 = tStream( pluck );
 var d2 = debug({
     'name': 'pluck'
 });
 var s3 = tStream( square );
 var d3 = debug({
     'name': 'square'
 });
 var s4 = tStream( toStr );
 var d4 = debug({
     'name': 'toString'
 });
 var s5 = tStream( join );
 var d5 = debug({
     'name': 'join'
 });
 
 // Create the pipeline:
 s1.pipe( d1 )
     .pipe( s2 )
     .pipe( d2 )
     .pipe( s3 )
     .pipe( d3 )
     .pipe( s4 )
     .pipe( d4 )
     .pipe( s5 )
     .pipe( d5 )
     .pipe( stdout );
 
 // 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 class="links">
 
 [stream]: https://nodejs.org/api/stream.html
 
 [object-mode]: https://nodejs.org/api/stream.html#stream_object_mode
 
 [transform-stream]: https://nodejs.org/api/stream.html
 
 [node-debug]: https://www.npmjs.com/package/debug
 
 </section>
 
 <!-- /.links -->