@johngw/stream/dist/transformers/timeout.js

Reactive programming tools using the WHATWG Streams API.

/**
 * Makes sure that events are emitted within `ms`.
 * Otherwise emits an error.
 *
 * @group Transformers
 * @throws {@link TimeoutError}
 * @example
 * readableStream
 *   .pipeThrough(timeout(1_000))
 *   .pipeTo(write())
 *   .catch(error => {
 *     // error is TimeoutError if any event took too long
 *   })
 */
export function timeout(ms) {
    let timer;
    return new TransformStream({
        start: (controller) => {
            begin(controller);
        },
        transform(chunk, controller) {
            begin(controller);
            controller.enqueue(chunk);
        },
        flush() {
            clearTimeout(timer);
        },
        cancel() {
            clearTimeout(timer);
        },
    });
    function begin(controller) {
        clearTimeout(timer);
        timer = setTimeout(() => controller.error(new TimeoutError(ms)), ms);
    }
}
/**
 * The error emitted from {@link timeout}.
 *
 * @group Transformers
 */
export class TimeoutError extends Error {
    ms;
    constructor(ms) {
        super(`Exceeded ${ms}ms`);
        this.ms = ms;
    }
}
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