pb.js

/******************************************************************************/
'use strict';
/******************************************************************************/
// progress bar as a module

module.exports = function pb(edge = 0) {
  const rl = require('readline');

  const DEFAULT_FREQ = 500;
  const HUNDRED_PERCENT = 100;
  const PB_LENGTH = 50;
  const PB_SCALE = HUNDRED_PERCENT / PB_LENGTH;

  const NANOSECONDS_PER_SECOND = 1e9;

  const hrStart = process.hrtime();

  function clearLine() {
    rl.cursorTo(process.stdout, 0);
    rl.clearLine(process.stdout, 0);
  }

  function getTimePast() {
    const hrEnd = process.hrtime(hrStart);
    return `${
      ((hrEnd[0] * NANOSECONDS_PER_SECOND + hrEnd[1]) / NANOSECONDS_PER_SECOND).toFixed(1)
    } s`;
  }

  return {
    edge,
    stat: 0,

    start(freq = DEFAULT_FREQ) {
      this.updater = setInterval(() => { this.update(); }, freq);
    },

    update(stat = this.stat) {
      const statPercent =
        stat === this.edge || stat > this.edge ?
        HUNDRED_PERCENT :
        stat / this.edge * HUNDRED_PERCENT;

      const barsNumber = Math.floor(statPercent / PB_SCALE);
      const padsNumber = PB_LENGTH - barsNumber;

      clearLine();
      process.stdout.write(
        `${'█'.repeat(barsNumber)}${'░'.repeat(padsNumber)} ${statPercent.toFixed(1)}%  ${getTimePast()} (${stat.toLocaleString()} of ${this.edge.toLocaleString()})`
      );
    },

    end() {
      clearInterval(this.updater);
      this.stat = this.edge;
      this.update();
      console.log('\n');
    },

    clear() {
      clearInterval(this.updater);
      clearLine();
    },
  };
};
/******************************************************************************/