docs: migrated from javascript to typescript (#2398)

docs/content/advanced/backend/subscribers/create-subscriber.md

@@ -4,36 +4,21 @@ In this document, you’ll learn how to create a [Subscriber](overview.md) in yo
 
 ## Prerequisites
 
-Medusa's event system works by pushing data to a Queue that each handler then gets notified of. The queuing system is based on Redis and you will therefore need to make sure that [Redis](https://redis.io) is installed and configured for your Medusa project.
+Medusa's event system works by pushing data to a Queue that each handler then gets notified of. The queuing system is based on Redis, so it's required for subscribers to work.
 
-Then, you need to set your Redis URL in your Medusa server. By default, the Redis URL is `redis://localhost:6379`. If you use a different one, set the following environment variable in `.env`:
-
-```bash
-REDIS_URL=<YOUR_REDIS_URL>
-```
-
-After that, in `medusa-config.js`, you’ll need to comment out the following line:
-
-```jsx
-module.exports = {
-  projectConfig: {
-    redis_url: REDIS_URL, //this line is commented out
-    ...
-  }
-}
-```
-
-After that, you are able to listen to events on your server.
+You can learn how to [install Redis](../../../tutorial/0-set-up-your-development-environment.mdx#redis) and [configure it with Medusa](../../../usage/configurations.md#redis) before you get started.
 
 ## Implementation
 
-After creating the file under `src/subscribers`, in the constructor of your subscriber, you should listen to events using `eventBusService.subscribe` , where `eventBusService` is a service injected into your subscriber’s constructor. 
+A subscriber is a TypeScript or JavaScript file that is created under `src/subscribers`. Its file name, by convension, should be the class name of the subscriber without the word `Subscriber`. For example, if the subscriber is `HelloSubscriber`, the file name should be `hello.ts`.
+
+After creating the file under `src/subscribers`, in the constructor of your subscriber, listen to events using `eventBusService.subscribe` , where `eventBusService` is a service injected into your subscriber’s constructor.
 
 The `eventBusService.subscribe` method receives the name of the event as a first parameter and as a second parameter a method in your subscriber that will handle this event.
 
 For example, here is the `OrderNotifierSubscriber` class which is created in `src/subscribers/orderNotifier.js`:
 
-```jsx
+```ts
 class OrderNotifierSubscriber {
   constructor({ eventBusService }) {
     eventBusService.subscribe("order.placed", this.handleOrder);
@@ -47,21 +32,21 @@ class OrderNotifierSubscriber {
 export default OrderNotifierSubscriber;
 ```
 
-This subscriber will register the method `handleOrder` as one of the handlers of the `order.placed` event. The method `handleOrder` will be executed every time an order is placed, and it will receive the order ID in the `data` parameter. You can then use the order’s details to perform any kind of task you need.
+This subscriber registers the method `handleOrder` as one of the handlers of the `order.placed` event. The method `handleOrder` will be executed every time an order is placed. It receives the order ID in the `data` parameter. You can then use the order’s details to perform any kind of task you need.
 
 :::note
 
-The `data` object will not contain other order data. Only the ID of the order. You can retrieve the order information using the `orderService`.
+The `data` object won't contain other order data. Only the ID of the order. You can retrieve the order information using the `orderService`.
 
 :::
 
 ## Using Services in Subscribers
 
-You can access any service through the dependencies injected to your subscriber’s constructor. 
+You can access any service through the dependencies injected to your subscriber’s constructor.
 
 For example:
 
-```jsx
+```ts
 constructor({ productService, eventBusService }) {
     this.productService = productService;