Web core Client - how to load Json from Xdata server direct into WebDBDataset/Grid

WEB TMS WEB Core
15

Okay the direct call works!
It must be used "FResult.text()"

Response := await (XDataWebClient1.RawInvokeAsync('ISQLQueryService.GetData', [params]) );
     asm
       //console.log(Response.FResult);
       JsText =await (Response.FResult.text());
     end;

But:
In my callback function the same code didn't work.

XDataWebClient1.RawInvoke('ISQLQueryService.GetData',[params],@onResponse);
...
...

Procedure TFormTest.onResponse(Response:TXDataClientResponse);
var JsText:String;
begin
     asm
       JsText = await (Response.FResult.text());
     end;

It gives the typeerror
TypeError: 'caller', 'callee', and 'arguments' properties may not be accessed on strict mode functions or the arguments objects for calls to them at Function.invokeGetter (:3:28) at Object.onResponse (http://localhost:8000/...