Simple Slack Incoming Webhook script for hubot to post useful messages (in pretty format) on channels/rooms. Also works without having hubot invited on the channel.

slack_post.js

/**
 * # Post messages using Slack's Webhook
 *
 * Use this in combination with node-cron to Schedule messages.
 * No need to have the hubot invited on the actual channel to post.
 *
 * ## Dependencies
 * 
 * superagent
 * lodash
 * 
 * ## How to use
 *
 * 1. Enable Incoming Webhook integration on slack.
 * 2. Set SLACK_WEBHOOK_URL with the webhook url from the enabled Slack integration
 * 3. Usage (in coffeescript):
 *
 *     # on init
 *     slack = require('slack_post')
 *         icon_emoji: ':calendar:'
 *         channel: '#another_slack_room'
 *         username: 'Calendar Post (via Hubot)'
 *
 *     # on message
 *     slack.post "Message"
 */

var request = require('superagent'),
    _ = require('lodash');

var defaultOptions = {
  channel: "#general",
  icon_emoji: ':ghost:',
  username: 'Hubot'
};

function ensureChannelName(channel) {
  return channel[0] === "#" ? channel : "#" + channel;
}

module.exports = function(options) {
  var url = process.env.SLACK_WEBHOOK_URL;

  return {
    post: function(text, attachments) {
      var postOptions = _.defaults({}, options, defaultOptions);

      postOptions.text = text;
      if (_.isArray(attachments) && attachments.length > 0) {
        postOptions.attachments = attachments;
      }

      request.post(url)
        .send(postOptions)
        .end(function (err, res) {
          console.error(err);
        });
    }
  }

}