node.jsでバイナリファイルの書き出し

var fs = require('fs');
var data = "write text test!";
var buf1 = new Buffer(108);
var initial = 0x873F;
var step = 0;
for (var j = 0 ; j < 6 ; j++) {
  for (var i = 0 ; i < 16 ; i++) {
    var char1 = i + initial + (16 * j);
    buf1[step++] = char1 & 0xFF;
    buf1[step++] = char1 >> 8;
  }
  buf1[step++] = 0x0D;
  buf1[step++] = 0x0A;
}

fs.writeFile('writetest.txt', buf1 , function (err) {
    console.log(err);
});

結果(writetest.txt)

?①②③④⑤⑥⑦⑧⑨⑩⑪⑫⑬⑭⑮�
O⑰⑱⑲⑳ⅠⅡⅢⅣⅤⅥⅦⅧⅨⅩ���
_㌔㌢㍍㌘㌧㌃㌶㍑㍗㌍㌦㌣㌫㍊㌻�
o㎝㎞�