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Streams/
TransformStream/

TransformStream

A TransformStream consists of a readable stream and a writable stream. It is designed based on the standard Web API TransformStream.

Constructor API

const { readable, writable } = new TransformStream(transformer?: any, writableStrategy?: WritableStrategy);

Parameters

Parameter
Type
Required
Description
transformer
any
No
This parameter is not supported. The values do not take effect and are ignored automatically.
writableStrategy
No
The strategy for the writable side.

WritableStrategy

Parameter
Type
Required
Description
highWaterMark
number
Yes
The size of the writable buffer in bytes. Default value: 32K. Maximum value: 256K. If you enter a value greater than 256K, the value is changed to 256K automatically.

Attributes

readable

readonly readable: ReadableStream;
The readable stream. For more information, see ReadableStream.

writable

readonly writable: WritableStream;
The writable stream. For more information, see WritableStream.

Sample Code

async function handleEnterRoom() {
  // Generate readable streams and writeable streams.
  const { readable, writable } = new TransformStream();
  // Fetch a remote resource. 
  const response = await fetch('https://www.tencentcloud.com/');
  // Respond to the client in streaming mode. 
  response.body.pipeTo(writable);

  return new Response(readable, response);
}

addEventListener('fetch', (event) => {
  event.respondWith(handleEvent(event));
});

References

MDN documentation: TransformStream
Sample Functions: Merging Resources and Responding in Streaming Mode
Sample Functions: Rewriting a m3u8 File and Configuring Authentication