TransformStreamDefaultController

const transformContent = {
  start() {}, // required.
  async transform(chunk, controller) {
    chunk = await chunk;
    switch (typeof chunk) {
      case "object":
        // just say the stream is done I guess
        if (chunk === null) controller.terminate();
        else if (ArrayBuffer.isView(chunk))
          controller.enqueue(
            new Uint8Array(chunk.buffer, chunk.byteOffset, chunk.byteLength),
          );
        else if (
          Array.isArray(chunk) &&
          chunk.every((value) => typeof value === "number")
        )
          controller.enqueue(new Uint8Array(chunk));
        else if (
          "function" === typeof chunk.valueOf &&
          chunk.valueOf() !== chunk
        )
          this.transform(chunk.valueOf(), controller); // hack
        else if ("toJSON" in chunk)
          this.transform(JSON.stringify(chunk), controller);
        break;
      case "symbol":
        controller.error("Cannot send a symbol as a chunk part");
        break;
      case "undefined":
        controller.error("Cannot send undefined as a chunk part");
        break;
      default:
        controller.enqueue(this.textencoder.encode(String(chunk)));
        break;
    }
  },
  flush() {
    /* do any destructor work here */
  },
};

class AnyToU8Stream extends TransformStream {
  constructor() {
    super({ ...transformContent, textencoder: new TextEncoder() });
  }
}