bin/slack.js

#!/usr/bin/env node
const { WebClient } = require('@slack/web-api');
const { Command } = require('commander');
const program = new Command();

program
    .arguments('<message>')
    .description( 'Sends a message to a slack channel.')
    .option('-d, --debug', 'output extra debugging')
    .option('-c, --channel <channel_id>', 'send message to slack channel', "dereko")
    .parse(process.argv);

const options = program.opts();
if (options.debug) console.log(options);

// An access token (from your Slack app or custom integration - xoxp, xoxb)
const token = process.env.SLACK_TOKEN;

const web = new WebClient(token);
const conversationId = options.channel;

(async () => {
  // See: https://api.slack.com/methods/chat.postMessage
  const res = await web.chat.postMessage({ channel: conversationId, text: program.args[0] });

  // `res` contains information about the posted message
  console.log('Message sent: ', res.ts);
})();