> ## Documentation Index
> Fetch the complete documentation index at: https://flatfileinc-remove-rss-json.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Setup a listener

> listen and respond to events in Flatfile

<Snippet file="shared/dxpbanner.mdx" />

Flatfile is an event-based system. This means that an
[Event](/learning-center/concepts/events) is published on almost any interaction a
user has within the Flatfile platform.

A [Listener](/learning-center/concepts/listeners) is a function that is triggered by an
Event. It's a powerful building block because it can be completely customized,
enabling you to respond to events precisely the way your business and workflow
require.

In this step of the tutorial, you'll learn how to set up a Listener to receive
Events.

## About listeners

Let's take a look at a basic listener.

<CodeGroup>
  ```js javascript theme={"system"}
  export default function (listener) {
    //note: listening to all events with a wildcard can be used while testing but is not 
    //recommended for production, as it will capture all events and may cause performance issues
    listener.on("**", (event) => {
      console.log(`Received event: ${event.topic}`);
    });
  }
  ```

  ```js typescript theme={"system"}
  import { FlatfileEvent, FlatfileListener } from "@flatfile/listener";

  export default function flatfileEventListener(listener: FlatfileListener) {
    //note: listening to all events with a wildcard can be used while testing but is not 
    //recommended for production, as it will capture all events and may cause performance issues
    listener.on("**", (event: FlatfileEvent) => {
      console.log(`Received event: ${event.topic}`);
    });
  }
  ```
</CodeGroup>

As you can see, this function is listening on "\*\*", which is a wildcard that
matches all events on all Apps. All this listener does is log an incoming
Event's topic.

## Setup your first listener

Let's walk through setting up your first listener. To do this, you'll be using
some of the tools Flatfile provides for developers.

<Info>
  Flatfile is a Typescript/Javascript platform, so you will need to install
  Node.js to use all the tools Flatfile provides developers. Though not
  required, switch to Node.js v18 for the best experience.
</Info>

First, clone our
[Getting Started](https://github.com/FlatFilers/getting-started) repository.

```terminal theme={"system"}
git clone https://github.com/FlatFilers/getting-started.git
```

Then, install dependencies.

<CodeGroup>
  ```ssh npm theme={"system"}
  npm install
  ```

  ```ssh yarn theme={"system"}
  yarn install
  ```
</CodeGroup>

Next, add your credentials. To do this, create an `.env` file at the root of your cloned repository.

```ssh theme={"system"}
cp .env.example .env
```

Now, update the `FLATFILE_API_KEY` value, setting it to your Secret Key.

## Run your first listener

Now that you have listener code configured with credentials, you're ready to
listen for Events.

We'll run this listener locally by using the "develop" command from the Flatfile
CLI.

You may chose to run either a Typescript or a Javascript version of this
listener:

<CodeGroup>
  ```terminal ts listener theme={"system"}
  npx flatfile@latest develop typescript/index.ts
  ```

  ```terminal js listener theme={"system"}
  npx flatfile@latest develop javascript/index.js
  ```
</CodeGroup>

Congratulations, you have created your first listener!

You should see console output that looks like this:

```ssh console theme={"system"}
> npx flatfile develop
✔ 1 environment(s) found for these credentials
✔ Environment "development" selected
ncc: Version 0.36.1
ncc: Compiling file index.js into CJS
  ✓ 427ms      GET    200 https://platform.flatfile.com/api/v1/subscription 12345

 File change detected. 🚀
  ✓ Connected to event stream for scope us_env_1234
```

***

## Next steps

To watch your listener receive an event, you'll need to trigger one. Let's learn
how to leverage your listener to
[Configure a Space](/learning-center/tutorials/projects/meet-the-workbook) on the fly.