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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6.1
ファクトリ
153
getRandomArray(1e6);
console.log('Done');
変数
p
に
Profiler
のインスタンスが保存されていますが、コードを見てもこの時点ではオブジェク
トがどのように生成、実装されているかわかりません。
上のコードを
profilerTest.js
という名前のファイルに入れて、次のコマンドを実行して確認し
てみましょう。
$ export NODE_ENV=development; node profilerTest
上のコマンドはコンソールにプロファイリング情報を出力します。模擬プロファイラのほうを試して
みたいなら、次のコマンドを実行します。
$ export NODE_ENV=production; node profilerTest
ここで示した例は、ファクトリ関数（メソッド）パターンの単純な応用ですが、オブジェクトの生成を
実装と分離する利点をはっきりと
示しています。
6.1.4
合成可能ファクトリ関数
Node
においてファクトリ関数をどのように実装するかわかったところで、
JavaScript
コミュニティで
人気となっている新しい高度なパターンを紹介しましょう。取り上げるのは「合成可能ファクトリ関数」
といって、複数のファクトリ関数から「合成」により機能拡張されたファクトリ関数を新たに生成できる
ようなタイプのものです。特に異なるオブジェクトから振る舞いやプロパティを継承するときに、複雑
なクラス階層を構築しなくてもオブジェクトを生成できるので便
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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.