@johngw/stream
Version:
Reactive programming tools using the WHATWG Streams API.
68 lines • 1.77 kB
JavaScript
import { pipeFlushes } from '@johngw/stream-common/Stream';
/**
* Runs every chunk through a predicate. If anything fails the
* predicate, `false` is queued and the stream terminated.
* Otherwise this will wait for the entire stream to finish
* before queuing `true`.
*
* @group Transformers
* @see {@link some:function}
* @example
* When every chunk passes the predicate.
* ```
* --1--2--3--4--5--6--7--8--9-|
*
* every((x) => x < 10)
*
* ----------------------------T-|
* ```
*
* When something fails the predicate.
* ```
* --1--2--3--4--5--6--X
*
* every((x) => x < 5)
*
* ------------------F-|
* ```
*
* A `flushes` stream can be used to force the transformer to queue
* it's current state downstream.
*
* ```
* --1--2--3--4--5--6--7--8--9-|
*
* every((x) => x < 10, { flushes:
* -----------N-----------------
* })
*
* -----------T----------------T-|
* ```
*/
export function every(predicate, options) {
const finishController = new AbortController();
return new TransformStream({
start(controller) {
pipeFlushes(() => controller.enqueue(true), (error) => controller.error(error), { ...options, signal: finishController.signal });
},
async transform(chunk, controller) {
try {
if (!(await predicate(chunk))) {
controller.enqueue(false);
controller.terminate();
}
}
catch (error) {
controller.error(error);
}
},
flush(controller) {
controller.enqueue(true);
finishController.abort();
},
cancel() {
finishController.abort();
},
});
}
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