docker-logs-localtime - Replace all UTC dates in docker logs output to local dates in pipe

docker-logs-localtime

#!/usr/bin/env node
/*
 * replace all UTC dates to local datetime with timezone offset through pipe
 * usage: docker logs -ft container_name | docker-logs-localtime
 *
 * Credits:
 *
 * docker-logs-localtime,
 * thank you anton-x-t,
 * https://gist.github.com/anton-x-t/859a69d0426ed1e4040660f57229c76c
 *
 * MDN Date, getMilliseconds(),
 * thank you MDN,
 * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date#date_components_and_time_zones 
 *
 * How to ISO 8601 format a Date with Timezone Offset in JavaScript?,
 * thank you Steven Moseley,
 * https://stackoverflow.com/a/17415677
 *
 * ISO 8601 - Wikipedia,
 * thank you Wikipedia Contributors,
 * https://en.wikipedia.org/wiki/ISO_8601
 *
 * docker-logs-localtime,
 * thank you popstas,
 * https://gist.github.com/popstas/ffcf282492fd78389d1df2ab7f31052a
 *
 * docker-logs-localtime,
 * thank you HuangYingNing,
 * https://github.com/HuangYingNing/docker-logs-localtime
 */
function toIsoString(date) {
  var tzo = -date.getTimezoneOffset(),
      dif = tzo >= 0 ? '+' : '-',
      pad = function(num) {
          return (num < 10 ? '0' : '') + num;
      };

  return date.getFullYear() +
      '-' + pad(date.getMonth() + 1) +
      '-' + pad(date.getDate()) +
      'T' + pad(date.getHours()) +
      ':' + pad(date.getMinutes()) +
      ':' + pad(date.getSeconds()) +
      '.' + pad(date.getMilliseconds()) +
      dif + pad(Math.floor(Math.abs(tzo) / 60)) +
      ':' + pad(Math.abs(tzo) % 60);
}

process.stdin.resume();
process.stdin.setEncoding('utf8');
process.stdin.on('data', function(data) {
  data = data.replace(/\d{2}:\d{2}:\d{2}\.\d{3} /g, '');
  const match = data.match(/\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d+Z/g);
  if (match) {
    match.forEach(dateUtc => {
      const dateLocal = toIsoString(new Date(dateUtc));
      data = data.replace(dateUtc, dateLocal);
    });
  }
  process.stdout.write(data);
});