#How to determine object variable type from a union?

3 messages · Page 1 of 1 (latest)

fossil pawn
# 
import { type} from "arktype";
const Account = type({name: "string"});
const Reminder = type({content: "string", due_at: "number"});
const Subtask = type({title: "string", completed_at: "number|null");
const Task = type([Subtask, "&", {subtasks: Subtask[]}]);

exists<T extends Account | Reminder | Task>(id: string, records: T[]) {
        for (let item of records) {
            if (item.id === id) {
                return true;
            }
            if (item is a Task) {
                for (let subtask of item.subtasks) {
                    if (subtask.id === id) {
                        return true
                    }
                }
            }
        }
        return false;
}```in this scenario, is there a way to do the `if (item is a Task)` check? I tried `if (item["subtasks"] !== undefined)` since `subtasks` is only a property of Task, but that gives an error saying it doesn't exist on the other types and so I can't index by it.
peak belfry
#

if ("subtasks" in item)

fossil pawn