JavaScript でジェネレータを使ってファイルを 1 行ずつ読み込んで処理する練習。

process-file-with-generator.js

const readline = require('readline');

async function processLineByLine(strm, eat) {
  const rl = readline.createInterface({
    input: strm,
    crlfDelay: Infinity
  });

  for await (const line of rl) {
    // Each line in input.txt will be successively available here as `line`.
    eat(false, line)
  }

  eat(true)
}

function eat(gen) {
  gen.next()
  return (done, line) => gen.next({done, line})
}

function* main() {
  while (true) {
    var {done, line} = yield
    if (done)
      break
    else
      console.log(">>>", line)
  }

  console.log("DONE!")
}

processLineByLine(process.stdin, eat(main()))