Function FormattedRelativeTime

packages/react-intl/components/relative.tsx:97–180

({
  value = 0,
  unit = 'second',
  updateIntervalInSeconds,
  ...otherProps
})

}

const FormattedRelativeTime: React.FC<Props> = ({
  value = 0,
  unit = 'second',
  updateIntervalInSeconds,
  ...otherProps
}) => {
  invariant(
    !updateIntervalInSeconds ||
      !!(updateIntervalInSeconds && canIncrement(unit)),
    'Cannot schedule update with unit longer than hour'
  )
  const [prevUnit, setPrevUnit] = React.useState<
    Intl.RelativeTimeFormatUnit | undefined
  >()
  const [prevValue, setPrevValue] = React.useState<number>(0)
  const [currentValueInSeconds, setCurrentValueInSeconds] =
    React.useState<number>(0)
  const updateTimer = React.useRef<number | undefined>(undefined)

  if (unit !== prevUnit || value !== prevValue) {
    setPrevValue(value || 0)
    setPrevUnit(unit)
    setCurrentValueInSeconds(
      canIncrement(unit) ? valueToSeconds(value, unit) : 0
    )
  }

  React.useEffect(() => {
    function clearUpdateTimer() {
      clearTimeout(updateTimer.current)
    }
    clearUpdateTimer()
    // If there's no interval and we cannot increment this unit, do nothing
    if (!updateIntervalInSeconds || !canIncrement(unit)) {
      return clearUpdateTimer
    }
    // Figure out the next interesting time
    const nextValueInSeconds = currentValueInSeconds - updateIntervalInSeconds
    const nextUnit = selectUnit(nextValueInSeconds)
    // We've reached the max auto incrementable unit, don't schedule another update
    if (nextUnit === 'day') {
      return clearUpdateTimer
    }

    const unitDuration = getDurationInSeconds(nextUnit)
    const remainder = nextValueInSeconds % unitDuration
    const prevInterestingValueInSeconds = nextValueInSeconds - remainder
    const nextInterestingValueInSeconds =
      prevInterestingValueInSeconds >= currentValueInSeconds
        ? prevInterestingValueInSeconds - unitDuration
        : prevInterestingValueInSeconds
    const delayInSeconds = Math.abs(
      nextInterestingValueInSeconds - currentValueInSeconds
    )

    if (currentValueInSeconds !== nextInterestingValueInSeconds) {
      updateTimer.current = setTimeout(
        () => setCurrentValueInSeconds(nextInterestingValueInSeconds),