I have a loadMore function that retrieves data and returns a Promise of either Project[] or Folder[] or undefined.
const items = await loadMore();
How can I specifically cast the type of 'items' to Folder[] in TypeScript?
I have a loadMore function that retrieves data and returns a Promise of either Project[] or Folder[] or undefined.
const items = await loadMore();
How can I specifically cast the type of 'items' to Folder[] in TypeScript?
In my opinion, it is more effective to distinguish the elements of the array by using an inline type discriminator as the condition in Array.filter
const folderItems = items?.filter(
(v: Folder | Project): v is Folder => /* Is v actually a Folder? true/false */
);
This will result in providing you with either an array that exclusively contains Folder items or undefined if the value of items is undefined.
Here's an alternative method you could use:
let folders: Folder[] = getFolders()
When working with TypeScript, one way to ensure type safety is through a type assertion:
const items = await loadMore() as Folder[];
However, it is recommended to utilize discriminated unions for enhanced safety.
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