Slack "Google Calendar for Teams" replacement

Google Calendar for Teams.gs

var webhookUrl = 'https://hooks.slack.com/services/XXXXXXXXXX/XXXXXXXXXX/XXXXXXXXXX'; // Webhook URL
var calendarId = '[email protected]'; // Id of the calendar
var slackChannel = '#team-calendar'; // Name of Slack channel to post updates to
var threshold = 30; // Seconds to look back after "onEventUpdated" event was received
var messageSingle = 'There is *1 event*';
var messageMultiple = 'There are *{events} events*';
var messageCreated = 'A *new event* has been created:';

function sendDailyEventsSummary() {
  sendEventsSummary(1, "today")
}

function sendWeeklyEventsSummary()
{
  sendEventsSummary(7, "this week")
}

function sendEventsSummary(numOfDays, periodDescriptor) {
  var start = new Date();
  start.setHours(0, 0, 0, 0);
  var end = new Date(start.getTime() + numOfDays * 24 * 60 * 60 * 1000);

  var events = Calendar.Events.list(calendarId, {
    timeMin: start.toISOString(),
    timeMax: end.toISOString(),
    singleEvents: true,
    orderBy: 'startTime'
  }).items;

  if (events.length === 0) {
    Logger.log('No events found.');
    return;
  }

  // Build the message
  var message = composeMessageHeader(events.length, periodDescriptor) 
  for (var event of events) {
    message += `\n\n` + formatEvent(event);
  }

  sendMessage(message);
}

function composeMessageHeader(eventCount, periodDescriptor) {
  if (eventCount == 1) {
    return `${messageSingle} ${periodDescriptor}`
  } else {
    return `${messageMultiple.replace('{events}', eventCount)} ${periodDescriptor}`;
  }
}

function onEventUpdated(e)
{
  var syncStartTime = new Date(new Date() - threshold * 1000);

  var events = CalendarApi.Events.list(calendarId, {
    updatedMin: syncStartTime.toISOString()
  }).items;

  for (var event of events) {
    if (event.status === 'cancelled') {
      // Event has been cancelled / deleted.
      continue;
    }

    var created = new Date(event.created);

    if (created < syncStartTime) {
      // Event has been created earlier and was only updated.
      continue;
    }

    sendMessage(messageCreated + '\n\n' + formatEvent(event));
  }
}

function formatEvent(event) {
  var result = `> *<${event.htmlLink}|${event.summary}>*\n`;
  if (event.start.date){
    result += `> ${(new Date(event.start.date)).toLocaleString('en-US', {dateStyle: 'full', timeStyle: 'short'})}`;
  } else if (event.start.dateTime) {
    result += `> ${(new Date(event.start.dateTime)).toLocaleString('en-US', {dateStyle: 'full', timeStyle: 'short'})}`;
  }

  if (event.location) {
    result += `\n> <https://maps.google.com/maps?q=${encodeURIComponent(event.location)}|${event.location}>`;
  }

  return result;
}

function sendMessage(message) {
  return UrlFetchApp.fetch(webhookUrl, {
    "method" : "post",
    "contentType" : "application/json",
    "payload" : JSON.stringify({
      "channel": "#events",
      "username": "Events",
      "text": message,
      "icon_emoji": ":calendar:"
    })
  });
}

Thanks for the script, but seems not work for me. I use calendar address var calendarId = '[email protected]';

11:15:00 AM Error
ReferenceError: Calendar is not defined
sendEventsSummary @ Code.gs:23
sendWeeklyEventsSummary @ Code.gs:15