Move Bytes to Record-Struct

In my Delphi VCL project I used the "Move" procedure to convert a byte array into a record struct. to load.
Source = array[0..2000] of byte;
Dest = recordstruct

move(Dest, Source, Count);

I have now recreated this function myself for webcore:

procedure byteMove(const Source; var Dest; Count: integer);
i : integer;
byteArray = array[0..2000] of byte;
for i := 0 to Count-1 do
byteArray(Dest)[i] := byteArray(Source)[i];
This procedure runs correctly under Delphi VCL under WebCore get an error.

TypeError: Dest.get is not a function | $mod.$implcode/$impl.byteMove@http://localhost...

rByte = array[0..2000] of byte;
rData = recordstruct


What possibilities are there in the WebCore to copy a memory area into another, the types of which are different?

This is not possible in a web browser application.
There is no such equivalent of mapping byte structures on records in JavaScript.
Memory and data types are handled in a completely different way in JavaScript so this mapping is unfortunately technically not possible.