time-ago

Utility to present in a human-readable format:

• time ago
• time in the future

Usage

ago = require("@weiseng18/time-ago")

// absolute time
ago.fromToday(1) // 52 years ago

// dynamic time (in the past)
ago.fromToday(new Date() - 7 * 24 * 60 * 60 * 1000) // 7 days ago
ago.fromToday(new Date() - 10 * 1000) // 10 seconds ago
ago.fromToday(new Date()) // just now

// dynamic time (in the future)
//
// interestingly, new Date() - 1000 will cast the new Date() to an integer
// however, new Date() + 1000 interprets appending "1000" to the date
// as such, need to do new Date().valueOf() instead
ago.fromToday(new Date().valueOf() + 1) // just now
ago.fromToday(new Date().valueOf() + 10 * 1000) // in 10 seconds
ago.fromToday(new Date().valueOf() - 7 * 24 * 60 * 60 * 1000) // in 7 days

Worked Example

Let initialTime be 31 Jan 2021 at 12PM GMT+8, and let today be 31 Mar 2021 at 12PM GMT+8.

Converting into epoch,

• initialEpoch (ms) is 1612065600000
• todayEpoch (ms) is 1617163200000

Calculating todayEpoch - initialEpoch to obtain timePassed, we obtain 5097600000 (ms).

Note that

• 5097600000 < 31536000000 = year in ms
• 5097600000 > 2628000000 = month in ms

From here we can tell that the largest unit of time where the elapsed time is still more than the unit, is month.

Dividing timePassed by the number of milliseconds in a month,

• 5097600000 / 2628000000 ≈ 1.9397
• Math.round(1.9397) = 2

Now we can conclude that initialTime was 2 months prior to today.

The util then returns "2 months ago".

Caveats

• The util uses Intl.RelativeTimeFormat, which only supports up to a smallest unit of seconds. For an absolute time less than 1 second ago, the util returns 'just now'.