Testing using a file stream for logging things

node_logger.js

const fs = require('fs');

function createLogger() {
  // const log_file = fs.createWriteStream(`${__dirname}/debug.log`, { flags: 'w' });
  const logStream = fs.createWriteStream('log.txt', { flags: 'a' });

  // logStream.log('Initial line...');
  // logStream.end('this is the end line');

  function formatDate(d) {
    return d
      .toISOString()
      .substring(0, 19)
      .replace('T', ' ');
  }

  const log = (message) => {
    const d = new Date();
    logStream.write(`${formatDate(d)} ${message}\n`);
  }

  return {
    log,
    end: logStream.end
  }
}

const a = createLogger();
a.log('a.1');

const b = createLogger();
b.log('b.1');

for (let i = 0; i < 10; i++) {
  const x = new Promise((resolve) => {
    a.log(`a.${i}`);
    b.log(`b.${i}`);

    resolve();
  });
}