This tutorial will guide you through the process of creating a simple Telegram bot that greets users. You will be using the **JavaScript** language and **Node.js** to write the code and the **GrammY** framework.

# Why GrammY?

There are several alternatives for the development of Telegram bots in JavaScript like [node-telegram-bot-api](https://github.com/yagop/node-telegram-bot-api) or [Telegraf](https://telegraf.js.org/). The first one is more just a library than a full-fledged framework. The second one is old and mature. But **GrammY** is relatively new, modern, and rapidly gaining popularity. 

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Furthermore, it has excellent documentation and a supportive community that can assist. And last but not least there is not a single article about **GrammY** on the **HackerNoon**, so let’s fix it!

# Meet the Hello Bot

We will develop a simple bot that can greet people in different languages. It’s a great example to learn how to process text messages and commands.

# Creating a bot and getting token

First, you need to create a bot account. To do this you need to use the [BotFather](https://t.me/BotFather). As the description says

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> BotFather is the one bot to rule them all. Use it to create new bot accounts and manage your existing bots.

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Open the bot, send `/newbot` command follow the instructions, create a bot and get a token.

# Project set up

As a prerequisite, you have to have **Node.js** installed. The easiest way is to download it from the [official site](https://nodejs.org/en/download/) and install it.

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The set up is usual for **Node.js** projects. Сreate an empty `grammy-hello-bot` folder open it in Terminal and run `npm init -y` command. Then install the **GrammY** package with `npm install grammy`. And create an empty `index.js` file. Eventually, you will get the following project structure.

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 ![Eventual project structure](https://cdn.hackernoon.com/images/ikJSOqfalLP8ugHSNVSmmK91QxJ3-hbb3pwl.png)

# The source code

Put the following code into the `index.js` file.

```javascript
const { Bot } = require('grammy');

const bot = new Bot(''); // <-- put your bot token here (https://t.me/BotFather)

bot.command('help', (ctx) => {
    ctx.reply(`
    The bot could greet people in different languages.
    The list of supported greetings:
    - hello - English
    - salut - French
    - hola - Spanish
    `)
});

bot.hears('salut', (ctx) => ctx.reply('salut'));
bot.hears('hello', (ctx) => ctx.reply('hello'));
bot.hears('hola', (ctx) => ctx.reply('hola'));

bot.on('message:text', (ctx) => ctx.reply(`Greeting "${ctx.update.message.text}" is not supported.`))

bot.start();
```

Let’s go line by line. First, we are requiring the **GrammY** module and creating an instance of our bot. It’s important to specify the bot token you got from the **BotFather** here.

```javascript
const { Bot } = require('grammy');

const bot = new Bot(''); // <-- put your bot token here (https://t.me/BotFather)
```

Now register a middleware to process `/help` command and to reply with instructions. Commands are just text messages that start with `/`, like `/start`, `/help` etc. You can come up with your own commands when you are developing a bot. And middlewares are just functions that process messages.

```javascript
bot.command('help', (ctx) => {
    ctx.reply(`
    The bot could greet people in different languages.
    The list of supported greetings:
    - hello - English
    - salut - French
    - hola - Spanish
    `)
});
```

The code above basically says: “If you got a message with `/help` command, just call this function and stop processing the message”. Meaning if one middleware processed a message, the other will not get a chance to do it. Middlewares are called one by one in the order they were registered.

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Then, using `hears` method we are registering middlewares that process different greetings and reply with it to the user.

```javascript
bot.hears('salut', (ctx) => ctx.reply('salut'));
bot.hears('hello', (ctx) => ctx.reply('hello'));
bot.hears('hola', (ctx) => ctx.reply('hola'));
```

And then a middleware that processes every text message that wasn’t processed by middlewares above. This middleware is necessary for the case when a user sends a greeting that is not supported by the bot.

```javascript
bot.on('message:text', (ctx) => ctx.reply(`Greeting "${ctx.update.message.text}" is not supported.`))
```

And then we are starting our bot. After that, it will begin to listen for messages from Telegram using a long-polling mechanism.

```javascript
bot.start();
```

Time to test it. Run the bot with `node index.js` command. Leave it running. Open **Telegram** and send something to the bot.

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 ![Sending messages to the bot](https://cdn.hackernoon.com/images/ikJSOqfalLP8ugHSNVSmmK91QxJ3-w8c3pa5.png)

# Links

* [GrammY documentation](https://grammy.dev/)
* [GrammY source code](https://github.com/grammyjs/grammY)
* [GrammY Telegram group](https://t.me/grammyjs)
* [Bots: An introduction for developers](https://core.telegram.org/bots)
* [Telegram Bot API documentation](https://core.telegram.org/bots/api/)

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The code in this story is for educational purposes. The readers are solely responsible for whatever they build with it.

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