如何获取user_id的“雪花”值？

// 定义各部分的位数
const timestampBits = 41;
const datacenterIdBits = 5;
const workerIdBits = 5;
const sequenceBits = 12;

// 定义起始时间戳（可以根据实际情况进行调整）
const startTimestamp = 1577808000000; // 2020-01-01 00:00:00 UTC

// 定义各部分的最大值
const maxDatacenterId = Math.pow(2, datacenterIdBits) - 1;
const maxWorkerId = Math.pow(2, workerIdBits) - 1;
const maxSequence = Math.pow(2, sequenceBits) - 1;

// 初始化各部分的值（可以根据实际情况进行调整）
let timestamp = Date.now() - startTimestamp;
let datacenterId = 1;
let workerId = 1;
let sequence = 0;

// 生成ID的方法
function generateId() {
  // 生成当前时间戳
  let currentTimestamp = Date.now() - startTimestamp;

  // 如果当前时间小于上次生成ID的时间，说明系统时间发生了回退，需要等待系统时间追上上次生成ID的时间
  if (currentTimestamp < timestamp) {
    // 等待时间差
    const offset = timestamp - currentTimestamp;

    // 如果等待时间小于等于5ms，则自旋等待
    if (offset <= 5) {
      while (Date.now() - startTimestamp < timestamp) {}
    } else {
      // 否则直接休眠等待
      sleep(offset);
    }

    currentTimestamp = Date.now() - startTimestamp;
  }

  // 如果是同一毫秒内生成的ID，则自增序列号
  if (currentTimestamp === timestamp) {
    sequence = (sequence + 1) & maxSequence;

    // 如果序列号已经达到最大值，则等待下一毫秒重新生成
    if (sequence === 0) {
      currentTimestamp = nextTimestamp(timestamp);
    }
  } else {
    // 否则，重置序列号
    sequence = 0;
  }

  // 更新上次生成ID的时间戳
  timestamp = currentTimestamp;

  // 生成最终的ID
  const id =
    (currentTimestamp << (datacenterIdBits + workerIdBits + sequenceBits)) |
    (datacenterId << (workerIdBits + sequenceBits)) |
    (workerId << sequenceBits) |
    sequence;

  return id.toString();
}

// 生成下一个时间戳
function nextTimestamp(lastTimestamp) {
  let currentTimestamp = Date.now() - startTimestamp;
  while (currentTimestamp <= lastTimestamp) {
    currentTimestamp = Date.now() - startTimestamp;
  }
  return currentTimestamp;
}

// 等待指定时间（使用异步方式）
function sleep(delay) {
  return new Promise((resolve) => setTimeout(resolve, delay));
}

// 示例用法
const user_id = generateId();
console.log(user_id);