Util function to select unit and value for the Intl.RelativeTimeFormat API

selectRelativeTimeUnit.js

export const UNITS = [
  {
    multiplier: 1000,
    name: 'second',
    threshold: 45,
  },
  {
    multiplier: 60,
    name: 'minute',
    threshold: 45,
  },
  {
    multiplier: 60,
    name: 'hour',
    threshold: 22,
  },
  {
    multiplier: 24,
    name: 'day',
    threshold: 5,
  },
  {
    multiplier: 7,
    name: 'week',
    threshold: 4,
  },
  {
    multiplier: 30,
    name: 'month',
    threshold: 4,
  },
  {
    multiplier: 30,
    name: 'quarter',
    threshold: 4,
  },
  {
    multiplier: 4,
    name: 'year',
    threshold: null,
  },
]

const selectRelativeTimeUnit = (to, from = Date.now(), config = {}) => {
  const { thresholds = {} } = config

  let diff = to - from
  let value = diff
  let unit = 'milliseconds'

  for (let u of UNITS) {
    const threshold = u.name in thresholds ? thresholds[u.name] : u.threshold

    value = value / u.multiplier
    unit = u.name

    if (typeof threshold !== 'number' || Math.abs(value) < threshold) {
      break
    }
  }

  if (Math.abs(value) < 1) {
    value = value > 0 ? 1 : -1
  } else {
    value = Math.round(value)
  }

  return {
    unit,
    value,
  }
}

export default selectRelativeTimeUnit

Thanks! Much better than having to fork DayJS' implementation

Similar library (for others on the internet finding this gist): https://www.npmjs.com/package/@formatjs/intl-utils