May 2019
Intermediate to advanced
464 pages
9h 22m
Japanese
Content preview from Node.jsデザインパターン 第2版
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5.2
ストリームの基本的な使い方
123
Hel
lo Node.js
!
実は第
5
のストリームとして
stream.PassThrough
があります。これまで見たストリー
ムクラスと違い、
PassThrough
は抽象型ではなく、メソッドを実装することなく直接的
にインスタンス化できます。このストリームは
Transform
ストリームで変換を適用せず
にすべてのデータチャンクを出力するものです。
5.2.6
パイプを使ったストリームの接続
Unix
の「パイプ」という概念を発明したのは
Douglas Mcllroy
ですが、これを使うことで、あるプロ
グラムの出力を次のプログラムの入力として簡単に接続できます。たとえば
Unix
系
OS
で次のコマンド
を実行してみてください。
$ echo Hello World! | sed s/World/Node.js/g
上のコマンドでは、まず
echo
が
Hello World!
を標準出力に書き込みます。続いて「
|
」があるた
め、
echo
の出力が
sed
コマンドの標準入力に渡されます（「リダイレクト」されます）。それから
sed
が
（最後に
g
があるため）文字列
World
のすべての出現を
Node.js
に置き換え、その結果を標準出力（こ
の場合コンソール）に出力します。
Node
のストリームも
Readable
ストリームのメソッド
pipe()
を使うことでこれと同じように接続で
きます。
pipe()
のシグニチャは次のとおりです。
readable.pipe(writable, [options]) ...
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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.