February 2013
Intermediate to advanced
380 pages
7h 45m
Japanese
Content preview from Nodeクックブック
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
312
9 章 自分の Node モジュールを作成する
lib/index.js
if(!(this instanceof Mp3dat)) {
return new Mp3dat(f, size);
}
これは、
new
でコンストラクタを呼び出してインスタンスを初期化するよりも少しだけ効率がよ
く、フェイルセーフでもある実装方法です。
本レシピでリファクタリングを行った
stat
メソッドは、レシピ
9.2
の
exports.stat
関数と
異なります。
exports.stat
では指定された
MP3
ファイルの名前とサイズを
findBitRate
と
buildStats
関数に渡しますが、本レシピの
stat
メソッドは
this
（
self
）を使って親オブジェクト
のメンバーオブジェクトに格納しています（コールバック関数で
this
が再設定されるため、
stat
メソッドの実行時に
this
は
self
に格納しておきます）。
stat
メソッドは
_findBitRate
と
_buildStats
メソッドを呼び出し、最終的に
stats
オブジェク
トの内容を計算し、パラメータに渡されたコールバック関数に渡します。
test.mp3
ファイルを指定して
mp3dat.stat
を実行すると、
mp3dat
モジュールオブジェクトは次
のような内容になります。
{ stats:
{ duration: { hours: 0, minutes: 0, seconds: 5, milliseconds: 186 },
bitrate: 128000,
filesize: ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.