Enhance TypeScript by optimizing the utilization of constructors within an array

I've managed to get this code working, but I'm convinced there's a more streamlined approach using rxjs. Can anyone shed some light on how I can simplify this? The main challenge here is that I need to invoke a custom constructor for each item in the array before returning it to the subscriber. (Running Angular 8.2.3, Typescript 3.5.3, and rxjs 6.4.0)

fetchItems() : Observable<Object>{
    const apiUrl = `${this.baseUrl}/items`;
    return this.http.get<Array<Item>>(apiUrl).pipe(
      map((itemList) => {
        itemList.forEach(function(item, index, array) {
          array[index] = new Item(item);
        });

        return itemList;
      }));
  }

Answer №1

Try utilizing the .map method within the .forEach callback instead of reassigning each index individually. This will allow you to transform every element into a Thing:

return this.http.get<Array<Thing>>(apiUrl).pipe(
  map(itemsArray => itemsArray.map(item => new Thing(item)))
);

Answer №2

Building on @CertainPerformance's suggestion, you can simplify your code by removing the type declaration in the function and letting TypeScript infer the type automatically.

In essence, your getAllthings() method will be streamlined to:

getAllthings = () =>
  this.http.get<Array<Thing>>(`${this.baseUrl}/things`).pipe(
      map(itemsArray => itemsArray.map(item => new Thing(item))
  )

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