@johngw/stream/dist/es/sinks/ForkableRecallSink.js

Reactive programming tools using the WHATWG Streams API.

import { empty } from '@johngw/stream-common/Symbol';
import { ForkableSink } from '@johngw/stream/sinks/ForkableSink';
/**
 * An extension to the {@link ForkableSink:class} that immediately
 * queues the last received chunk to any fork.
 *
 * @group Sinks
 * @see {@link ForkableRecallStream:class}
 * @example
 * ```
 * const forkable = new ForkableRecallSink<number>()
 * const writable = new WritableStream(forkable)
 * await fromCollection([1, 2, 3, 4, 5, 6, 7]).pipeTo(writable)
 * ```
 *
 * Now the stream has finished, if we fork from it we'll
 * receive the last thing that was emitted.
 *
 * ```
 * await forkable.fork().pipeTo(write(console.info))
 * // 7
 * ```
 */
export class ForkableRecallSink extends ForkableSink {
    #chunk = empty;
    write(chunk) {
        this.#chunk = chunk;
        return super.write(chunk);
    }
    _addController(underlyingSource, queuingStrategy) {
        const [controller, stream] = super._addController(underlyingSource, queuingStrategy);
        if (this.#chunk !== empty)
            controller.enqueue(this.#chunk);
        return [controller, stream];
    }
}
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