如何从给定城市的给定日期和时间获取以秒为单位的unix纪元时间戳？

import datetime
import pytz

def get_unix_timestamp(city, date_str, time_str):
    # Step 1: Determine the city's timezone
    timezone = pytz.timezone(city)

    # Step 2: Convert to UTC time
    dt = datetime.datetime.strptime(date_str + ' ' + time_str, '%Y-%m-%d %H:%M:%S')
    dt = timezone.localize(dt)
    utc_dt = dt.astimezone(pytz.utc)

    # Step 3: Convert to Unix timestamp
    unix_timestamp = (utc_dt - datetime.datetime(1970, 1, 1, tzinfo=pytz.utc)).total_seconds()
    return int(unix_timestamp)

# Usage example
city = 'Asia/Shanghai'
date_str = '2022-01-01'
time_str = '12:34:56'
unix_timestamp = get_unix_timestamp(city, date_str, time_str)
print(unix_timestamp)

const moment = require('moment-timezone');

function getUnixTimestamp(city, dateStr, timeStr) {
  // Step 1: Determine the city's timezone
  const timezone = moment.tz.zone(city);

  // Step 2: Convert to UTC time
  const dt = moment.tz(`${dateStr} ${timeStr}`, 'YYYY-MM-DD HH:mm:ss', timezone.name);
  const utcDt = dt.utc();

  // Step 3: Convert to Unix timestamp
  const unixTimestamp = Math.floor(utcDt.valueOf() / 1000);
  return unixTimestamp;
}

// Usage example
const city = 'Asia/Shanghai';
const dateStr = '2022-01-01';
const timeStr = '12:34:56';
const unixTimestamp = getUnixTimestamp(city, dateStr, timeStr);
console.log(unixTimestamp);