https://github.com/mafintosh/peek-stream

Transform stream that lets you peek the first line before deciding how to parse it
https://github.com/mafintosh/peek-stream

Last synced: 9 days ago
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Transform stream that lets you peek the first line before deciding how to parse it

• Host: GitHub
• URL: https://github.com/mafintosh/peek-stream
• Owner: mafintosh
• License: mit
• Created: 2014-07-23T15:17:38.000Z (over 10 years ago)
• Default Branch: master
• Last Pushed: 2023-03-31T11:29:03.000Z (over 1 year ago)
• Last Synced: 2024-10-16T23:40:26.987Z (23 days ago)
• Language: JavaScript
• Size: 8.79 KB
• Stars: 56
• Watchers: 4
• Forks: 5
• Open Issues: 3
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# peek-stream

Transform stream that lets you peek the first line before deciding how to parse it

```

npm install peek-stream

```

[![build status](http://img.shields.io/travis/mafintosh/peek-stream.svg?style=flat)](http://travis-ci.org/mafintosh/peek-stream)

![dat](http://img.shields.io/badge/Development%20sponsored%20by-dat-green.svg?style=flat)

## Usage

``` js

var peek = require('peek-stream')

var ldjson = require('ldjson-stream')

var csv = require('csv-parser')

var isCSV = function(data) {

  return data.toString().indexOf(',') > -1

}

var isJSON = function(data) {

  try {

    JSON.parse(data)

    return true

  } catch (err) {

    return false

  }

}

// call parser to create a new parser

var parser = function() {

  return peek(function(data, swap) {

    // maybe it is JSON?

    if (isJSON(data)) return swap(null, ldjson())

    // maybe it is CSV?

    if (isCSV(data)) return swap(null, csv())

    // we do not know - bail

    swap(new Error('No parser available'))

  })

}

```

The above parser will be able to parse both line delimited JSON and CSV

``` js

var parse = parser()

parse.write('{"hello":"world"}\n{"hello":"another"}\n')

parse.on('data', function(data) {

  console.log(data) // prints {hello:'world'} and {hello:'another'}

})

```

Or

``` js

var parse = parser()

parse.write('test,header\nvalue-1,value-2\n')

parse.on('data', function(data) {

  console.log(data) // prints {test:'value-1', header:'value-2'}

})

```

Per default `data` is the first line (or the first `65535` bytes if no newline is found).

To change the max buffer pass an options map to the constructor

``` js

var parse = peek({

  maxBuffer: 10000

}, function(data, swap) {

  ...

})

```

If you want to emit an error if no newline is found set `strict: true` as well.

## License

MIT