Improve typescript for using constructors on an array

Question

I have the following code that is working, but I feel like there is a much simpler way of doing this with rxjs. Does anyone know how this can be simplified? The main reason for the complexity is I need to run the custom constructor on each item in the array before I can return it to the subscribing method. (Angular 8.2.3, Typescript 3.5.3, rxjs 6.4.0)

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

        return itemsArray;
      }));
  }

CertainPerformance · Accepted Answer · 2020-12-09 16:13:38Z

4

Instead of reassigning each index inside the .forEach callback, use .map instead, to transform every element into a Thing:

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

answered Dec 9, 2020 at 16:13

CertainPerformance

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1 Comment

dmoore1181 Over a year ago

Thank you for this, I knew there was something simple I was missing.

Owen Kelvin · Accepted Answer · 2020-12-09 16:36:26Z

0

An addition to @CertainPerformance solution, you can remove type declaration on the function and let typescript infer the type

Overally your getAllthings() will reduce to

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

answered Dec 9, 2020 at 16:36

Owen Kelvin

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