@johngw/stream/dist/es/transformers/debounce/Transformer.js

Reactive programming tools using the WHATWG Streams API.

/**
 * The transformer implementation for {@link debounce:function}.
 *
 * @group Transformers
 * @see {@link debounce:function}
 */
export class DebounceTransformer {
    #behaviors;
    #state;
    constructor(ms, behaviors) {
        this.#behaviors = behaviors;
        this.#state = this.#reduceState('init', { ms, queued: false });
    }
    transform(chunk, controller) {
        this.#preTimer(chunk, controller);
        this.#timer(chunk, controller);
    }
    flush() {
        clearTimeout(this.#state.timer);
    }
    #preTimer(chunk, controller) {
        clearTimeout(this.#state.timer);
        this.#state = this.#reduceState('preTimer', {
            ...this.#state,
            queued: false,
        }, chunk, controller);
    }
    #timer(chunk, controller) {
        this.#state = {
            ...this.#state,
            timer: setTimeout(() => this.#postTimer(chunk, controller), this.#state.ms),
        };
    }
    #postTimer(chunk, controller) {
        clearTimeout(this.#state.timer);
        this.#state = this.#reduceState('postTimer', {
            ...this.#state,
            timer: undefined,
        }, chunk, controller);
    }
    #reduceState(stage, state, chunk, controller) {
        return this.#behaviors.reduce((state, behavior) => 
        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
        behavior[stage]?.(state, chunk, controller) || state, state);
    }
}
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