package.json

{
  "name": "uuidv1",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "level": "^6.0.1",
    "level-rocksdb": "^4.0.0",
    "uuid": "^8.3.0"
  }
}

test.js

const {v1} = require("uuid");
const rocksdb = require("level-rocksdb");
const rdb = rocksdb("./rocksdb", { keyEncoding: "binary", valueEncoding: "utf-8" });
const level = require("level");
const db = level("./codes", { keyEncoding: "binary", valueEncoding: "utf-8" });
const start = 5;
for(let i = start; i < start+3; i++) {
  const key = Buffer.alloc(20, "code");
  v1(null, key, 4);
  console.log(i, key.toString("ascii", 0, 4), new Date(v1time(key, 4)));
  rdb.put(key, i, err => err ? console.error(err) : console.log(`rocks write ${i}`));
  db.put(key, i, err => err ? console.error(err) : console.log(`level write ${i}`));
}
setTimeout(async() => {
  console.log("leveldb");
  const stream = db.createReadStream({ limit: 1000 });
  for await (const data of stream) {
      console.log(data.key, new Date(v1time(data.key, 4)), data.value);
  }
  console.log("rocksdb");
  const stream2 = rdb.createReadStream({ limit: 1000 });
  for await (const data of stream2) {
      console.log(data.key, new Date(v1time(data.key, 4)), data.value);
  }
}, 1000);

function v1time(buf, offset) {
    let msec = 0, nsec = 0;
    let i = buf && offset || 0;
    let b = buf||[];

    // inspect version at offset 6
    if ((b[i+6]&0x10) !== 0x10)
        throw new Error("uuid version 1 expected");

    // 'time_low'
    let tl = 0;
    tl |= ( b[i++] & 0xff ) << 24;
    tl |= ( b[i++] & 0xff ) << 16;
    tl |= ( b[i++] & 0xff ) << 8;
    tl |=   b[i++] & 0xff ;

    // `time_mid`
    let tmh = 0;
    tmh |= ( b[i++] & 0xff ) << 8;
    tmh |=   b[i++] & 0xff;

    // `time_high_minus_version`
    tmh |= ( b[i++] & 0xf ) << 24;
    tmh |= ( b[i++] & 0xff ) << 16;

    // account for the sign bit
    msec = ((tl >>> 1) * 2 + ((tl & 0x7fffffff) % 2)) / 10000.0;
    msec += ((tmh >>> 1) * 2 + ((tmh & 0x7fffffff) % 2)) * 0x100000000 / 10000.0;

    // Per 4.1.4 - Convert from Gregorian epoch to unix epoch
    msec -= 12219292800000;

    // getting the nsec. they are not needed now though
    // nsec = ( tl & 0xfffffff ) % 10000;

    return msec;
}