Tinkering with reading large file, line by line, and running async function in Node.js

index.coffee

# http://stackoverflow.com/questions/11078141/how-to-run-an-async-function-for-each-line-of-a-very-large-1gb-file-in-node
readVeryLargeFile = (path) ->
  ids       = []
  i         = 0
  remaining = ''

  onData = (chunk) ->
    # this will add new chunk to potential fragment from previous onData stream
    remaining  += chunk.toString()
    lines       = remaining.split("\n")
    last        = lines.pop() # can't assume last line is a full line.
    remaining   = last # remaining.substr(remaining.lastIndexOf(last))
    i           = lines.length

    stream.pause()

    iterate = (line, next) ->
      parts = line.split(/[\t\s]+/)
      throw new Error(line) unless parts[2]
      id    = parts[2]

      console.log id

      setTimeout next, 10

    async.forEachSeries lines, iterate, ->
      stream.resume()

  stream  = fs.createReadStream(path, flags: 'r', encoding: 'utf-8', bufferSize: 1024 / 4)
  stream.on('data', onData)

readVeryLargeFile('tmp/test.csv')