kitten.sh
1import { TalkbackFn, TeardownFn, Start, Push, SignalKind } from './types';
2
3/** Placeholder {@link TeardownFn | teardown functions} that's a no-op.
4 * @see {@link TeardownFn} for the definition and usage of teardowns.
5 * @internal
6 */
7export const teardownPlaceholder: TeardownFn = () => {
8 /*noop*/
9};
10
11/** Placeholder {@link TalkbackFn | talkback function} that's a no-op.
12 * @privateRemarks
13 * This is frequently used in the codebase as a no-op initializer value for talkback functions in
14 * the implementation of {@link Operator | Operators}. This is cheaper than initializing the
15 * variables of talkbacks to `undefined` or `null` and performing an extra check before calling
16 * them. Since the {@link Start | Start signal} is assumed to come first and carry a talkback, we can
17 * use this to our advantage and use a no-op placeholder before {@link Start} is received.
18 *
19 * @internal
20 */
21export const talkbackPlaceholder: TalkbackFn = teardownPlaceholder;
22
23/** Wraps the passed {@link TalkbackFn | talkback function} in a {@link Start | Start signal}.
24 * @internal
25 */
26export function start<T>(talkback: TalkbackFn): Start<T> {
27 const box: any = [talkback];
28 box.tag = SignalKind.Start;
29 return box;
30}
31
32/** Wraps the passed value in a {@link Push | Push signal}.
33 * @internal
34 */
35export function push<T>(value: T): Push<T> {
36 const box: any = [value];
37 box.tag = SignalKind.Push;
38 return box;
39}