Node.js: conditional file streams

Writable file stream that can write to different files based upon the condition of what's being written. i.e. Intead of passing filePath as the first parameter to your stream, you pass a function that returns the path.

This saves you time because you no longer have to manage many different writable streams.

Use Case

Best use case is to only have one writable fs stream that writes log files, except the log file path changes depending up the date or log data.

Usage

npm i --save cfs

Example 1

Write log data to different files depending upon the date.

var cfs = require('cfs')
var path = require('path')
var ymd = require('ymd')

var pathFn = function () {
  // get date in YYYY-MM-dd
  var date = ymd(new Date())
  return path.join('/tmp/logs/' + date + '.txt')
}

var logWriter = cfs.createWriteStream(pathFn, { flags: 'a' })
logWriter.write(someLogData)

Example 2

Write data to different files depending upon what's being written. Write even numbers to evens.txt and odd numbers to odds.txt.

No need to worry about opening a bunch of files. File descriptors are cached.

var cfs = require('cfs')

var pathFn = function (data) {
  if (data == null) return null

  if (parseInt(data.toString('utf8'), 10) % 2 === 0) {
    return 'evens.txt'
  } else {
    return 'odds.txt'
  }
}

var logWriter = cfs.createWriteStream(pathFn, { flags: 'a' })
logWriter.write(someLogData)

API

createWriteStream()

• pathFunction: A function that should return the path. Method signature (data, encoding).
• options: These are the standard options that you'd pass to fs.createWriteStream. Also, cacheOptions which are the options that you'd pass to lru-cache.

License

MIT

Copyright (c) JP Richardson