javascript Object.type中是否有属性

我现在正在研究Node.Js，发现了这段代码：

  var combine = require('stream-combiner');
  var through = require('through2');
  var split = require('split');
  var zlib = require('zlib');
  module.exports = function () {
      var grouper = through(write, end);
      var current;
      function write (line, _, next) {
          if (line.length === 0) return next();
          var row = JSON.parse(line);
          if (row.type === 'genre') {
             if (current) {
                 this.push(JSON.stringify(current) + ''n');
             }
              current = { name: row.name, books: [] };
          }
          else if (row.type === 'book') {
              current.books.push(row.name);
          }
          next();
      }
      function end (next) {
          if (current) {
              this.push(JSON.stringify(current) + ''n');
          }
          next();
      }
      return combine(split(), grouper, zlib.createGzip());
  };

write函数得到的每一行都是一个json行，如下所示：

"name": "Neuromancer","genre": "cyberpunk"

预期的结果是以下JSON对象：

{
"name": "cyberpunk",
"books": [
  "Accelerando",
  "Snow Crash",
  "Neuromancer",
  "The Diamond Age",
  "Heavy Weather"
]}

等等。

基本上我的问题是row.type是什么意思？

提前感谢！：D