https://github.com/thlorenz/tap-stream

Taps a nodejs stream and logs the data that's coming through
https://github.com/thlorenz/tap-stream

Last synced: about 1 month ago
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Taps a nodejs stream and logs the data that's coming through

• Host: GitHub
• URL: https://github.com/thlorenz/tap-stream
• Owner: thlorenz
• Created: 2012-10-03T02:09:02.000Z (about 12 years ago)
• Default Branch: master
• Last Pushed: 2016-05-19T12:36:13.000Z (over 8 years ago)
• Last Synced: 2024-11-02T01:42:07.523Z (about 2 months ago)
• Language: JavaScript
• Homepage:
• Size: 306 KB
• Stars: 14
• Watchers: 3
• Forks: 1
• Open Issues: 2
• Metadata Files:
  • Readme: README.md

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README

        
# tap-stream [![Build Status](https://secure.travis-ci.org/thlorenz/tap-stream.png)](http://travis-ci.org/thlorenz/tap-stream)

Taps a nodejs stream and logs the data that's coming through.

    npm install tap-stream

Given an [object stream](#object-stream) we can print out objects passing through and control the detail via the

depth parameter:

```javascript

objectStream().pipe(tap(0));

```

![depth0](https://github.com/thlorenz/tap-stream/raw/master/assets/depth0.png)

```javascript

objectStream().pipe(tap(1));

```

![depth1](https://github.com/thlorenz/tap-stream/raw/master/assets/depth1.png)

```

objectStream().pipe(tap(2));

```

![depth2](https://github.com/thlorenz/tap-stream/raw/master/assets/depth2.png)

For even more control a custom log function may be supplied:

```javascript

objectStream()

  .pipe(tap(function customLog (data) {

      var nest = data.nest;

      console.log ('Bird: %s, id: %s, age: %s, layed egg: %s', nest.name, data.id, nest.age, nest.egg !== undefined);

    })

  );

```

```text

Bird: yellow rumped warbler, id: 0, age: 1, layed egg: true

Bird: yellow rumped warbler, id: 1, age: 1, layed egg: true

```

## API

### tap( [ depth | log ] )

Intercepts the stream and logs data that is passing through.

- optional parameter is either a `Number` or a `Function`

- if no parameter is given, `depth` defaults to `0` and `log` to `console.log(util.inspect(..))`

- `depth` controls the `depth` with which

  [util.inspect](http://nodejs.org/api/util.html#util_util_inspect_object_showhidden_depth_colors) is called

- `log` replaces the default logging function with a custom one

**Example:**

```javascript

var tap = require('tap-stream');

myStream

  .pipe(tap(1)) // log intermediate results

  .pipe(..)     // continute manipulating the data

```

## Object stream

Included in order to give context for above examples.

```javascript

function objectStream () {

  var s = new Stream()

    , objects = 0;

 

  var iv = setInterval(

      function () {

        s.emit('data', { 

            id: objects

          , created: new Date()

          , nest: { 

                name: 'yellow rumped warbler'

              , age: 1

              , egg: { name: 'unknown' , age: 0 }

              } 

          }

        , 4

        );

        if (++objects === 2) {

            s.emit('end');

            clearInterval(iv);

        }

      }

    , 200);

  return s;

}

```