Simple Progress Reporter for JavaScript

progress.js

// gets time now in milliseconds
const msNow = () => (+new Date())

function createProgress ({
  maxItems = 100,
  onProgressChange = () => {},
  onComplete = () => {}
}) {
  let currentProgress = 0 // %
  let lastProgress = 0

  const startTimeInMs = msNow()
  let msPassedFromLastProggress = 0
  let lastProgressStartedAt = msNow()

  return {
    report (count) {
      currentProgress = (count / maxItems) * 100
      const progressChangedSignificantly = Math.floor(currentProgress) > Math.floor(lastProgress)

      if (progressChangedSignificantly) {
        msPassedFromLastProggress = (msNow() - lastProgressStartedAt)
        lastProgressStartedAt = msNow()

        onProgressChange({
          progress: Math.floor(currentProgress) + '%',
          msPassed: msPassedFromLastProggress + 'ms'
        })

        const finalProgressReport = currentProgress === 100

        if (finalProgressReport) {
          const totalTimeTakenMs = msNow() - startTimeInMs

          onComplete({
            totalTimeTakenMs: totalTimeTakenMs
          })
        }
      }

      lastProgress = currentProgress
    }
  }
}

module.exports = createProgress

/* USAGE EXAMPLE
const progress = createProgress({
    maxItems: 1000,
    onProgressChange: ({progress, msPassed}) => console.info(`${progress} in ${msPassed}`),
    onComplete: ({ totalTimeTakenMs }) => console.info(chalk.blue(`Total time taken: ${totalTimeTakenMs}ms`))
})

progress.report(currentItemNumber) //e.g. 420 would cause it to output 42%

*/