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Slack bot with Nodejs

·3 mins
Table of Contents

Build your slack bot in a few steps. In this post, we’ll navigate the process of creating the bot.

Slack setup #

First, create a slack workspace

  • Give your workspace a name

create_workspace

Create a new bot at slack apps

  • Give your new application a name
  • Choose the workspace you created before installing the bot application

create_app

Then go to the Features > OAuth & Permissions screen to scroll down to Bot Token Scopes to specify the OAuth scopes, and select app_mentions and chat_write to enable the bot to send messages.

add_oauth

Before jumping into the application setup, copy the signing secret and verification token from the basic information page. We’ll be using this later in our NodeJS application.

secret_token

Application setup #

Create an npm project, install @slack/bolt and dotenv packages

mkdir test-bot && cd test-bot
npm init -y
npm i dotenv @slack/bolt -S

Add start command to scripts if necessary.

...
"scripts": {
  "start": "node index.js"
}

Create a .env file and add SLACK_SIGNING_SECRET, SLACK_BOT_TOKEN

Note: Don’t commit this file to any repo

SLACK_BOT_TOKEN= #token goes here
SLACK_SIGNING_SECRET= #signing secret goes here

In your index.js file, require the Bolt package, and initialize an app with credentials.

require("dotenv").config();
const { App } = require("@slack/bolt");

const bot = new App({
  signingSecret: process.env.SLACK_SIGNING_SECRET,
  token: process.env.SLACK_BOT_TOKEN,
  endpoints: "/slack/events",
});

(async () => {
  // Start the app
  await bot.start(process.env.PORT || 3000);

  console.log("⚡️ Bolt app is running!");
})();

Deploy the application to a live server like ngrok.

Event Setup #

We’ll need to subscribe to events so that when a Slack event happens (like a user mentions an app), the app server will receive an event payload.

  • Go to Event Subscriptions from the left-hand menu, and turn the toggle switch on to enable events

  • Enter your Request URL

enable_events

Subscribe to app_mention event

event_subscribe

Install app to workspace

install_app_workspace

You should see the bot in your workspace now!

Handling Events #

To listen to any Events API events from Slack, use the event() method. This method allows your app to take action on Slack events. In this scenario, it’s triggered when a user mentions the app.

bot.event("app_mention", async ({ context, event }) => {
  try {
    const command = event.text;
    let reply;
    if (command.includes("Hi")) {
      reply = `Hi <@${event.user}>,  you mentioned me`;
    } else {
      reply = "How can I help you?";
    }
    await bot.client.chat.postMessage({
      token: context.botToken,
      channel: event.channel,
      text: `${reply}`,
    });
  } catch (e) {
    console.log(`error responding ${e}`);
  }
});

Okay, let’s try the app!

Add the app to a channel and mention the app. You should see a response from the bot!

Troubleshooting #

Reinstall the app if you don’t see any responses from the bot

reinstall_app

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