estimate job completion time in JS

job-completion-estimate.js

// To run: node job-completion-estimate

function sleep() {
  return new Promise((resolve) => {
    // add a random jitter of +-0.5 seconds
    setTimeout(() => resolve(), 1000 - (Math.random() - 0.5) * 1000);
  });
}

function humanReadableTime(duration) {
  const milliseconds = parseInt((duration % 1000) / 100, 10);
  const seconds = Math.floor((duration / 1000) % 60);
  const minutes = Math.floor((duration / (1000 * 60)) % 60);
  const hours = Math.floor((duration / (1000 * 60 * 60)) % 24);

  return `${hours} hour(s) ${minutes} minute(s) ${seconds}.${milliseconds} second(s)`;
}

const numberOfJobs = 100;

async function main() {
  const initTime = new Date();
  let totalTimeSpent = 0;

  for (let i = 1; i <= numberOfJobs; i += 1) {
    const start = new Date();
    await sleep();
    const end = new Date();
    const elapsedTime = end - start;  // in milliseconds
    // CR + clear line
    process.stdout.write('\r\x1b[2K');
    process.stdout.write(`Elapsed time: ${elapsedTime}ms\t|| `);
    totalTimeSpent += elapsedTime;
    const remainingJobs = numberOfJobs - i;
    const avgTimeSpent = totalTimeSpent / i;
    const estimate = humanReadableTime(avgTimeSpent * remainingJobs);
    process.stdout.write(`Remaining job count: ${remainingJobs} => time remaining estimate: ${estimate}`);
  }
  return initTime;
}

main()
  .then((startTime) => {
    const end = new Date();
    const elapsedTime = end - startTime;  // in milliseconds
    console.log(`\nElapsed time: ${elapsedTime}ms`);
  });