FutureObject := TTask.Future<Integer>(function: Integer
    begin
        Sleep(3000);
        Result := 16;
    end);
// …
MyValue := FutureObject.Value;

unit Unit23;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, WebView2, Winapi.ActiveX, Vcl.Edge;

type
  TForm23 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

  TExecuteScriptCallBack = procedure(Value: string) of object;

  TExecuteScript = class
    Result: string;
    procedure OnExecuteScript(Value: string);
    procedure ExecuteScript(Script: string; CallBack: TExecuteScriptCallBack);
  end;

var
  Form23: TForm23;

implementation

uses
  System.Threading;

{$R *.dfm}

procedure TExecuteScript.ExecuteScript(Script: string; CallBack: TExecuteScriptCallBack);
begin
  Sleep(1000);
  CallBack('Ok');
end;

procedure TExecuteScript.OnExecuteScript(Value: string);
begin
  Result:=Value;
end;

{ TForm23 }

procedure TForm23.Button1Click(Sender: TObject);
begin
  var ExecuteScript:=TTask.Future<string>(function: string begin
                       var ES:=TExecuteScript.Create;
                       try
                         ES.ExecuteScript('test',Es.OnExecuteScript);
                         repeat
                           Sleep(1);
                         until ES.Result<>'';
                         Result:=ES.Result;
                       finally
                         ES.Free;
                       end;
                     end);


  ShowMessage(ExecuteScript.Value);
end;

end.