Slack "Google Calendar for Teams" replacement

Google Calendar for Teams.gs

var webhookUrl = 'https://hooks.slack.com/services/…/…/…'; // Webhook URL
var calendarId = '…@group.calendar.google.com'; // Id of the calendar
var slackChannel = '#events'; // Name of Slack channel to post updates to
var threshold = 30; // Seconds to look back after "onEventUpdated" event was received
var messageWeeklySingle = 'There is *1 event* this week:';
var messageWeeklyMultiple = 'There are *{events} events* this week:';
var messageCreated = 'A *new event* has been created:';

function sendWeeklyEventsSummary()
{
  var start = new Date();
  start.setHours(0, 0, 0, 0);
  var end = new Date(start.getTime() + 7 * 24 * 60 * 60 * 1000);

  var events = CalendarApi.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 = events.length === 1 ? messageWeeklySingle : messageWeeklyMultiple.replace('{events}', events.length);
  for (var event of events) {
    message += `\n\n` + formatEvent(event);
  }

  sendMessage(message);
}

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`;
  result += `> ${(new Date(event.start.dateTime)).toLocaleString('de-AT', {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:"
    })
  });
}

@mburtscher thanks for this!
I forked your code and made some minor update

• I added a daily summary function.
• I fixed a bug where it wasn't handling date vs dateTime properly`
• I made the message creation a little bit more dynamic

You can see it here if you are interested:
https://gist.github.com/ogoldberg/9a807342ed1c508800e62a64b75ba623