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

Reactive programming tools using the WHATWG Streams API.

/**
 * Hold up a stream until a promise resolves. If it errors,
 * the error will be emitted to the stream.
 *
 * @group Transformers
 * @example
 * ```
 * ----a-------b------|
 *
 * interpose(async () => await setTimeout(50))
 *
 * --------a--------b-|
 * ```
 */
export function interpose(promise) {
    const fn = typeof promise === 'function' ? promise : () => promise;
    return new TransformStream({
        async transform(chunk, controller) {
            try {
                await fn(chunk);
            }
            catch (error) {
                return controller.error(error);
            }
            controller.enqueue(chunk);
        },
    });
}
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