# Intl Utils Provide i18n utilities. [![npm Version](https://img.shields.io/npm/v/@formatjs/intl-utils.svg?style=flat-square)](https://www.npmjs.org/package/@formatjs/intl-utils) ## API ### selectUnit This function determines the `best fit` unit based on a specific set of customizable thresholds. ```ts function selectUnit( from: Date | number, to: Date | number = Date.now(), thresholds = DEFAULT_THRESHOLDS ): {value: number; unit: Unit}; ``` where `thresholds` has the shape of: ```ts interface Threshold { second: number; minute: number; hour: number; day: number; } ``` `month` & `year` are based on calendar, thus not customizable. Example: ```ts import {selectUnit} from '@formatjs/intl-utils'; selectUnit(Date.now() - 1000); // { value: -1, unit: 'second' } selectUnit(Date.now() - 44000); // { value: -44, unit: 'second' } selectUnit(Date.now() - 50000); // { value: 1, unit: 'minute' } ``` #### Caveats `selectUnit` is meant to be a stepping stone from the old `IntlRelativeFormat` to the officially spec-ed `Intl.RelativeTimeFormat`. Therefore we don't recommend using this for an extended period of time because of ambiguous editorial issues such as: - From 2019/01/01 -> 2018/11/01 can technically be `last year`, `2 months ago` or `a quarter ago`. - From 2019/01/02 6am to 2019/01/01 11pm can also be `7 hours ago` or `yesterday`. Timezone further complicates the issue. The examples above have not even tackled the differences in non-Gregorian calendars. There is an issue opened upstream in the spec that potentially introduces a [`best fit` algorithm](https://github.com/tc39/proposal-intl-relative-time/issues/47). Therefore, we recommend that you implement your own version of `selectUnit` that matches your editorial expectation.