Why are nested RxJS map operators used and how do they impact data transformation?

Recently, I enrolled in an online Angular course and discovered that RxJS plays a significant role in web development. While exploring different concepts, I encountered a nested map operator that intrigued me. Although I can somewhat decipher what is happening, my search for detailed information on this topic has been fruitless.

    this.productService.getProducts().pipe(
      map(products => 
        products.map(product => {
          const data = {...product.payload.val() as Product}; 
          return data;
        }))).subscribe(p => this.products = p)

As far as my understanding goes, the getProducts() function returns a list of Observables. The outer map operator then passes each individual Observable to the inner map operator, enabling me to extract the payload data from the HTTP response. However, I can't help but wonder if there is a simpler or more elegant way to achieve this functionality.

Answer №1

Exploring RxJS can lead to a fascinating journey once you dive into it.

It looks like the getProducts() method returns an Observable that emits an array of Products stored within product.payload.val.

By using the map function, the payload from getProducts() is transformed into a typed array of Products.

This conversion could also be achieved with the following code snippet:

this.productService.getProducts().pipe(
      map(products => {...product.payload.val() as Product[]})
)

https://stackblitz.com/edit/typescript-3jed7f?file=index.ts

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