# Streams

> How Elide supports ReadableStream, WritableStream and TransformStream per the Streams Standard, including byte streams, BYOB readers and `from()`.

`ReadableStream`, `WritableStream`, `TransformStream`, their readers, writers, and controllers,
`CountQueuingStrategy`, and `ByteLengthQueuingStrategy` are globals. They follow the
[Streams Standard](https://streams.spec.whatwg.org/), including byte streams, BYOB readers, and `ReadableStream.from()`.

## Example

```js
// webstreams.mjs
const numbers = ReadableStream.from([1, 2, 3, 4]);
const doubled = numbers.pipeThrough(
  new TransformStream({
    transform(n, controller) {
      controller.enqueue(n * 2);
    },
  }),
);

const seen = [];
await doubled.pipeTo(
  new WritableStream({
    write(n) {
      seen.push(n);
    },
  }),
);
console.log(seen.join(" "));

const text = await new Response(ReadableStream.from(["he", "llo"]).pipeThrough(new TextEncoderStream())).text();
console.log(text);
```

`elide run webstreams.mjs` prints:

```text
2 4 6 8
hello
```

## Differences from browsers

- A stream cannot be transferred to a worker: naming one in a `postMessage` transfer list throws `DataCloneError`.

For byte transforms, see [Compression Streams](https://elide.help/docs/api-whatwg-compression).

<!-- api-reference:start 68d53f55bc9d -->
## Reference

**Status:** Full · Not measured · since 1.1.0

### Exports

| Export | Kind | Status | Notes |
| --- | --- | --- | --- |
| `ReadableStream` | class | Full | `locked`, `cancel()`, `getReader()`, `pipeThrough()`, `pipeTo()`, `tee()` |
| `ReadableStreamDefaultReader` | class | Full | `closed`, `read()`, `releaseLock()`, `cancel()` |
| `ReadableStreamDefaultController` | class | Full | `desiredSize`, `close()`, `enqueue()`, `error()` |
| `ReadableStreamBYOBReader` | class | Full | `closed`, `read()`, `releaseLock()`, `cancel()` |
| `ReadableByteStreamController` | class | Full | `byobRequest`, `desiredSize`, `close()`, `enqueue()`, `error()` |
| `ReadableStreamBYOBRequest` | class | Full | `view`, `respond()`, `respondWithNewView()` |
| `WritableStream` | class | Full | `locked`, `abort()`, `close()`, `getWriter()` |
| `WritableStreamDefaultWriter` | class | Full | `closed`, `desiredSize`, `ready`, `abort()`, `close()`, `releaseLock()`, `write()` |
| `WritableStreamDefaultController` | class | Full | `signal`, `error()` |
| `TransformStream` | class | Full | `readable`, `writable` |
| `TransformStreamDefaultController` | class | Full | `desiredSize`, `enqueue()`, `error()`, `terminate()` |
| `CountQueuingStrategy` | class | Full | `highWaterMark`, `size` |
| `ByteLengthQueuingStrategy` | class | Full | `highWaterMark`, `size` |
<!-- api-reference:end -->