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WIP observables
WIP observables

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observable.ts
68 lines | 2.4 KiB | video/mp2t | TypeScriptLexer
import { isPromise } from "@implab/core-amd/safe";
import { Unsubscribable, Producer, Observable, Subscribable } from "./observable/interfaces";
import { ObservableImpl } from "./observable/ObservableImpl";
export const isUnsubscribable = (v: unknown): v is Unsubscribable =>
v !== null && v !== undefined && typeof (v as Unsubscribable).unsubscribe === "function";
export const isSubscribable = <T = unknown>(v: unknown): v is Subscribable<T> =>
v !== null && v !== undefined && typeof (v as Subscribable<unknown>).subscribe === "function";
export const observe = <T>(producer: Producer<T>): Observable<T> => new ObservableImpl<T>(producer);
/** Converts an array to the observable sequence of its elements. */
export const ofArray = <T>(items: T[]): Observable<T> => new ObservableImpl<T>(
({ next, complete }) => (
items.forEach(next),
complete()
)
);
/** Converts a subscribable to the observable */
export const ofSubscribable = <T>(subscribable: Subscribable<T>) =>
observe<T>(sink => {
const subscription = subscribable.subscribe(sink);
return () => subscription.unsubscribe();
});
const of1 = <T>(item: T | PromiseLike<T>) => observe<T>(
({ next, error, complete }) =>
isPromise(item) ?
void item.then(
v => (next(v), complete()),
error
) :
(next(item), complete())
);
/** Converts a list of parameter values to the observable sequence. The
* order of elements in the list will be preserved in the resulting sequence.
*/
export const of = <T>(...items: (T | PromiseLike<T>)[]) => items.length === 1 ?
of1(items[0]) :
observe<T>(
({ next, error, complete, isClosed }) => {
const n = items.length;
const _next = (start: number) => {
if (start > 0 && isClosed()) // when resumed
return;
for (let i = start; i < n; i++) {
const r = items[i];
if (isPromise(r)) {
r.then(v => (next(v), _next(i + 1)), error);
return; // suspend
} else {
next(r);
}
}
complete();
};
_next(0);
}
);
export const empty: Observable<never> = new ObservableImpl<never>(({ complete }) => complete());
export type * from "./observable/interfaces";