ago.ts

/**
 * Human readable elapsed or remaining time (example: 3 minutes)
 * modified from https://stackoverflow.com/a/67338038/938822
 */

const rft = new Intl.RelativeTimeFormat(
	typeof navigator !== 'undefined' ? [...navigator?.languages] : ['en'],
	{ numeric: 'auto' }
)

export function ago(
	/** A Date object, timestamp or string parsable with Date.parse() */
	date: string | number | Date,
	/** A Date object, timestamp or string parsable with Date.parse() */
	nowDate: string | number | Date = Date.now()
): string {
	const SECOND = 1000
	const MINUTE = 60 * SECOND
	const HOUR = 60 * MINUTE
	const DAY = 24 * HOUR
	const WEEK = 7 * DAY
	const MONTH = 30 * DAY
	const YEAR = 365 * DAY
	const intervals = [
		{ ge: YEAR, divisor: YEAR, unit: 'year' },
		{ ge: MONTH, divisor: MONTH, unit: 'month' },
		{ ge: WEEK, divisor: WEEK, unit: 'week' },
		{ ge: DAY, divisor: DAY, unit: 'day' },
		{ ge: HOUR, divisor: HOUR, unit: 'hour' },
		{ ge: MINUTE, divisor: MINUTE, unit: 'minute' },
		{ ge: 0, divisor: SECOND, unit: 'seconds' },
	]
	const now = typeof nowDate === 'object' ? nowDate.getTime() : new Date(nowDate).getTime()
	const diff = now - (typeof date === 'object' ? date : new Date(date)).getTime()
	const diffAbs = Math.abs(diff)
	for (const interval of intervals) {
		if (diffAbs >= interval.ge) {
			const x = Math.round(Math.abs(diff) / interval.divisor)
			const isFuture = diff < 0
			return rft.format(isFuture ? x : -x, interval.unit as Intl.RelativeTimeFormatUnit)
		}
	}
}