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~ ReadableStreamDefaultReader.cancel()

The **`cancel()`** method of the
`ReadableStreamDefaultReader` interface returns a `Promise` that resolves when the stream is canceled. Calling this method signals a loss of interest in the stream by a consumer.

Cancel is used when you've completely finished with the stream and don't need any more
data from it, even if there are chunks enqueued waiting to be read. That data is lost
after cancel is called, and the stream is not readable any more. To read those chunks
still and not completely get rid of the stream, you'd use
`ReadableStreamDefaultController.close()`.

> **Note:** If the reader is active, the
> `cancel()` method behaves the same as that for the associated stream
> (`ReadableStream.cancel()`).

## Syntax

```js
cancel()
cancel(reason)
```

### Parameters

- `reason` _**optional**_
  - : A human-readable reason for the cancellation. This value may or may not be used.

### Return value

A `Promise`, which fulfills with the value given in the `reason`
parameter.

### Exceptions

- `TypeError`
  - : The source object is not a `ReadableStreamDefaultReader`, or the stream
    has no owner.
