Shows the amount of time elapsed since a timestamp, with pretty formatting

showTimeElapsed.js

const showTimeElapsed = (timestamp) => {
  if (typeof timestamp !== 'number') return 'NaN'

  const SECOND = 1000
  const MINUTE = SECOND * 60
  const HOUR = MINUTE * 60
  const DAY = HOUR * 24
  const MONTH = DAY * 30
  const YEAR = MONTH * 12

  const elapsed = ((new Date()).valueOf() - timestamp)

  if (elapsed <= MINUTE) return `${Math.round(elapsed / SECOND)}s`
  if (elapsed <= HOUR) return `${Math.round(elapsed / MINUTE)}m`
  if (elapsed <= DAY) return `${Math.round(elapsed / HOUR)}h`
  if (elapsed <= MONTH) return `${Math.round(elapsed / DAY)}d`
  if (elapsed <= YEAR) return `${Math.round(elapsed / MONTH)}mo`
  return `${Math.round(elapsed / YEAR)}y`
}

console.log(showTimeElapsed(1541309742360))