Slackのチャンネル一覧を定期実行するためのGAS

ChannelGuide.js

// エントリーポイント
function ChannelGuide() {
  var channels = fetchChannles();
  postSlack(channels);
}

// APIトークン
var token = 'thisissecret';
// Incoming WebhookのURL
var webhookUrl = 'thisissecret';
var channelsUrl = 'https://slack.com/api/channels.list?token=' + token + '&exclude_archived=1&pretty=1';
// 除外するチャンネル
var excludePatterns = ['times_.*', 'general', 'random'];

function fetchChannles() {
  var channels = JSON.parse(UrlFetchApp.fetch(channelsUrl)).channels;
  Logger.log(channels);
  var filterdChannels = [];
  for (var i = 0; i < channels.length; i++) {
    var channel = channels[i];
    var exclude = false;
    for (var j = 0; j < excludePatterns.length; j++) {
      var excludePattern = excludePatterns[j]
      pattern = new RegExp(excludePattern);
      if (channel.name.match(pattern)) {
        exclude = true;
        break;
      }
    }
    if (!exclude) {
      filterdChannels.push(channel);
    }
  }
  return filterdChannels;
}

function postSlack(channels) {
  if (channels.length <= 0) {
    return;
  }
  var baseUrl = webhookUrl;
  var headers = {
    'Content-Type': 'application/json'
  };
  var params = {
    'channel': '#random',
    'username': '番組表',
    'icon_emoji': ':tokyo_tower:',
    'text': createPostMessage(channels),
  }
  var options = {
    'method': 'POST',
    'headers' : headers,
    'payload': JSON.stringify(params)
  };
  UrlFetchApp.fetch(baseUrl, options);
}

function createPostMessage(channels) {
  var message = ':zap:チャンネル一覧:zap:(気になるチャンネルに参加してみましょう！)\n';
  for (var i = 0; i < channels.length; i++) {
    var channel = channels[i];
    message += '<#' + channel.id + '|' + channel.name +  '>';
    if (channel.purpose) {
        message += ' ' + channel.purpose.value;
    }
    message += '\n';
  }
  return message;
}

• SlackのAPIトークン
• Incoming webhookのURL
• 除外するチャンネルリスト

を設定したら動きます！