命令型 vs 宣言型プログラミング

• Imperative programming: telling the "machine" how to do something, and as a result what you want to happen will happen.
• Declarative programming: telling the "machine"1 what you would like to happen, and let the computer figure out how to do it.

例えば指定されたフォルダー内の.coffeeファイルを表示する簡単なコードを書きます。

命令型：

fs = require 'fs'
path = require 'path'

dirName = process.argv[2]
dirContents = fs.readdirSync dirName

files = (path.resolve(dirName, file) for file in dirContents when file.indexOf('.coffee') isnt -1)

console.log files

宣言型：

fs = require 'fs'
path = require 'path'

dirName = process.argv[2]
dirContents = fs.readdirSync dirName

files = dirContents
  .filter((file) -> file.indexOf('.coffee') isnt -1)
  .map((file) -> path.resolve(dirName, file))

console.log files