Itest = interface(IDispatch)
    ['{D9941302-C827-4517-ADA0-003D176E9E9A}']
function Method1(const a: WideString): OleVariant; stdcall;
end;

type
  Ttest = class(TAutoObject, Itest)
protected
function Method1(const fd: WideString): OleVariant; stdcall;

end;

implementation

uses ComServ;

function Ttest.Method1(const fd: WideString): OleVariant;
begin

end;

var a=window.external.Method1('fdsa');
alert(a);

Itest = interface(IDispatch)
    ['{D9941302-C827-4517-ADA0-003D176E9E9A}']
function Method1(const a: WideString): OleVariant; safecall;
end;

  Ttest = class(TAutoObject, Itest)
protected
 function Method1(const a: WideString): OleVariant; safecall;

end;

implementation

uses ComServ;

function Ttest.Method1(const a: WideString): OleVariant;
begin

end;