liner.js

var Transform = require('stream').Transform;

function Liner() {
  Transform.call(this, { objectMode: true });
}

Liner.prototype = {
  _transform: function (chunk, encoding, done) {
    var data = chunk.toString()
    if (this._lastLineData) data = this._lastLineData + data

    var lines = data.split('\n')
    this._lastLineData = lines.splice(lines.length - 1, 1)[0]

    lines.forEach(this.push.bind(this))
    done()
  },
  _flush: function (done) {
    if (this._lastLineData) this.push(this._lastLineData)
    this._lastLineData = null
    done()
  }
}

extend(Transform, Liner);

function extend(base, sub) {
  // Avoid instantiating the base class just to setup inheritance
  // See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create
  // for a polyfill
  // Also, do a recursive merge of two prototypes, so we don't overwrite
  // the existing prototype, but still maintain the inheritance chain
  // Thanks to @ccnokes
  var origProto = sub.prototype;
  sub.prototype = Object.create(base.prototype);
  for (var key in origProto) {
    sub.prototype[key] = origProto[key];
  }
  // Remember the constructor property was set wrong, let's fix it
  sub.prototype.constructor = sub;
  // In ECMAScript5+ (all modern browsers), you can make the constructor property
  // non-enumerable if you define it like this instead
  Object.defineProperty(sub.prototype, 'constructor', {
    enumerable: false,
    value: sub
  });
}

module.exports = Liner;