How do you transmit raw byte data in Javascript/Typescript?

[sketch34]

I need to send raw binary data to a typescript client. How to do this?

table Row{
  payload: [uint8];
}

But in Typescript flatc turns this into an array of number:

public payload: (number)[] = []

Does this mean there is an 8x space overhead for each byte in the Typescript flatbuffer? Considering in C++ this is a flatbuffers::Vector<uint8_t> I'm not quite sure how this is compatible over the wire.

Update

I just spotted Row.payloadArray() which appears to return the data as a Uint8Array. This is what I need I think.

Looks like the RowT payload uses createScalarList() to convert the underlying byte array to a number array. If speed / mem are critical probably best to avoid this activating function, i.e. avoid using the Object API when transferring byte arrays in JS/TS.

Update 2

I can't figure out how to get a union in Typescript when not using the Object API. Not sure what the accessor function should be.

          let px_msg = PxMsg.getSizePrefixedRootAsPxMsg(new flatbuffers.ByteBuffer(data));
          expect(px_msg.msgType).toBe(Message.Snapshot);

          let accessor = ???;   // Which function do I reference / bind here?

          let s = unionToMessage(Message.Snapshot, accessor) as Snapshot;

[sketch34]

I forgot to post final solution (to "update 2") once I figured it out:

union Message {
  MyMessageType,
  ...
}


table MyRootMsg {
  msg: Message;  // Message is a union.
}

flatc will generate this as part of the MyRootMsg type:

msg<T extends flatbuffers.Table>(obj:any):any|null {
  const offset = this.bb!.__offset(this.bb_pos, 6);
  return offset ? this.bb!.__union(obj, this.bb_pos + offset) : null;
}

which we can use as the "accessor":

let root_msg = MyRootMsg.getSizePrefixedRootAsMyRootMsg(new flatbuffers.ByteBuffer(data));

// Must bind to set 'this' correctly for function object.
let accessor = root_msg.msg.bind(root_msg);

let m = unionToMessage(Message.MyMessageType, accessor) as MyMessageType;

Good candidate for adding to the docs.