getTLIdEncoderDecoder.js - Locally unique, shorter, sortable timestamp based Id's
June 17, 2013 —
Matt Forrester
I have recently wrote getTLIdEncoderDecoder.js which is a component of SyncIt's upcoming Path based storage.
Given a supplied epoch it will generate you TLId, which is a word I just invented!
What is a TLId? It stands for Time Local Id and gives you a reference based on a timestamp that is locally unique.
Advantages:
- The are shorter than timestamps (though not by a lot).
- You can extract the timestamp that the TLId was generated.
- If you want them ordered by generation time, you do not need to convert them back to timestamps beforehand.
Here's how you use it:
// Use one character (32 bit number) to ensure uniqueness within a millisecond
var uniquenessPerMillisecond = 1;
// As close as possible (but lower) than the lowest date to give shorter Id's
var epoch = new Date(1970,0,1).getTime();
// Get the TLId Encoder / Decoder
var encoderDecoder = getTLIdEncoderDecoder(epoch,uniquenessPerMillisecond);
// Encode a date into a unique string
var dates = [
encoderDecoder.encode(),
encoderDecoder.encode(new Date(1980,1,6).getTime()),
encoderDecoder.encode(new Date(1981,3,15).getTime()),
encoderDecoder.encode(new Date(1986,8,9).getTime()),
encoderDecoder.encode(new Date(1983,10,3).getTime()),
encoderDecoder.encode(new Date(1982,0,6).getTime())
];
// Get the dates it was encoded
var originalTimestamps = dates.map(encoderDecoder.decode);
// Sort them in date order
var sortedDates = dates.sort(encoderDecoder.sort);