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cancel(reason)
The cancel()
method of the ReadableStream interface returns a Promise
that resolves when the stream is canceled.
Cancel is used when you’ve completely finished with the stream and don’t need any more data from it, even if chunks are enqueued waiting to be read. That data is lost after cancel
is called, and the stream is not readable any more. To close the stream without getting rid of enqueued chunks, use ReadableStreamDefaultController.close().
Arguments
Name | Type | Description |
---|---|---|
reason | any | An optional human-readable value that represents the reason for canceling the stream. |
Return value
A promise that resolves with the value undefined
when the stream is canceled.
Exceptions
Exception | Description |
---|---|
TypeError | Thrown the stream is locked to a reader. |
Example
JavaScript
import { ReadableStream } from 'k6/experimental/streams';
import { setTimeout } from 'k6/timers';
export default async function () {
// Define a number stream that emits numbers from 1 to 10 every second
const stream = numbersStream();
const reader = stream.getReader();
while (true) {
const { done, value } = await reader.read();
if (done) break;
if (value === 8) {
// Cancel the stream when the number is 8, any enqueued chunks are lost
await reader.cancel('cancelling the stream');
break;
}
}
}
function numbersStream() {
let currentNumber = 0;
return new ReadableStream({
start(controller) {
const fn = () => {
if (currentNumber < 10) {
controller.enqueue(++currentNumber);
setTimeout(fn, 1000);
return;
}
controller.close();
};
setTimeout(fn, 1000);
},
});
}
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