Support custom unit option of relativeTime

[ktmouk]

Is your feature request related to a problem? Please describe.

format.relativeTime currently only supports returning a relative time using an automatically calculated unit in this function.
However, there may be cases that we sometimes want to use a specific unit to develop an application.

For example, if we were to create a timeline UI that groups photos by date in a photo album app, we might want to specify the day unit when creating a title for the timeline, since, with other units, it might get too detailed.

Describe the solution you'd like

One solution I came up with is to add a unit argument to relativeTime function, like this:

const dateTime = new Date('2020-11-20T00:00:00Z');
const now = new Date('2020-11-20T01:00:00Z');

const format = useFormatter();
format.relativeTime(dateTime, now, 'day');  // returns 'today', not '1 hour'

Describe alternatives you've considered

We can also use RelativeTimeFormat directly instead:

console.log(new Intl.RelativeTimeFormat('en', { numeric: 'auto' }).format(0, 'day')); // 'today'

[amannn]

Seems like a good enhancement, yes!

API-wise I have two thoughts:

1. Maybe we should accept an object, in case we allow to configure further properties in the future. E.g. {unit: 'day'}.
2. now is an optional parameter, maybe we should overload the second argument to avoid something like format.relativeTime(dateTime, undefined, {unit: 'day'}).

Based on this, format.relativeTime(dateTime: Date, nowOrOptions: Date | {now?: Date, unit?: string}) could be an idea.

What do you think? Would you be interested in contributing this feature and the corresponding docs?

[ktmouk]

Thank you for your reply! Your idea is superior to mine. I would like to contribute to this.