Asynchronously iterate over a CSV file one line at a time

readCSV.js

function readCSV(filename, eachCallback, doneCallback) {
  var error;

  var reader = require('readline').createInterface({
    input: require('fs').createReadStream(filename),
    output: null,
    terminal: false
  });

  reader.on('line', function(line) {
    if (!line) return;

    var self = this;
    this.pause();

    var parts;
    if (line[0] === '"') {
      line = line.substr(1, line.length - 2);
      parts = line.split('","');
    } else {
      parts = line.split(',');
    }

    // Unescape quotes
    for (var i = 0; i < parts.length; i++)
      parts[i] = parts[i].replace(/\\"/g, '"');

    eachCallback(parts, function(err) {
      if (err) {
        error = err;
        return self.close();
      }
      self.resume();
    });
  });

  reader.on('error', doneCallback);

  reader.on('close', function() {
    doneCallback(error);
  });
}