Function to send an AWS CloudWatch alarm message to Slack

function.js

console.log('Loading function');

const https = require('https');
const url = require('url');
// to get the slack hook url, go into slack admin and create a new "Incoming Webhook" integration
const slack_url = 'https://hooks.slack.com/services/...';
const slack_req_opts = url.parse(slack_url);
slack_req_opts.method = 'POST';
slack_req_opts.headers = {'Content-Type': 'application/json'};

exports.handler = function(event, context) {
  (event.Records || []).forEach(function (rec) {
    if (rec.Sns) {
      var req = https.request(slack_req_opts, function (res) {
        if (res.statusCode === 200) {
          context.succeed('posted to slack');
        } else {
          context.fail('status code: ' + res.statusCode);
        }
      });
      
      req.on('error', function(e) {
        console.log('problem with request: ' + e.message);
        context.fail(e.message);
      });
      
      //Parse the CloudWatch alarm message and only post the StateValue and AlarmName to keep it clean.
      var messageObj = JSON.parse(rec.Sns.Message);
      var emoji = "";
      switch (messageObj.NewStateValue){
          case "ALARM":
              emoji = ":alarm_clock: ";
              break;
          case "OK":
              emoji = ":white_check_mark: ";
              break;
          case "INSUFFICIENT_DATA":
              emoji = ":information_source: ";
              break;
      }
      req.write(JSON.stringify({text: emoji + messageObj.NewStateValue + ": " + messageObj.AlarmName})); // for testing: , channel: '@vadim'
      
      req.end();
    }
  });
};

Modified the original from vgeshel to parse a CloudWatch alarm message into a more readable format.

Added emoji based on NewStateValue

Removed double JSON.stringify to prevent quotes from showing up in the Slack message