Pascal (Lazarus/Delphi)

Call a JavaScript Function Passing an Object Argument

See more JavaScript Examples

Demonstrates how to call a JavaScript function with an argument that is an object. Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.Js,
  Chilkat.StringBuilder,
  Chilkat.JsonArray,
  Chilkat.JsonObject;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  sbScript: TStringBuilder;
  js: TJs;
  result: TJsonObject;
  funcCall: TJsonObject;
  arg: TJsonObject;
  argsArray: TJsonArray;
  sbOut: TStringBuilder;

begin
  success := False;

  //  This is the JavaScript function we'll call:

  //  function describeCar(car) {
  //  	console.log(`This is a ${car.year} ${car.make} ${car.model}.`);
  //  }

  sbScript := TStringBuilder.Create;
  sbScript.Append('function describeCar(car) { console.log(`This is a ${car.year} ${car.make} ${car.model}.`); }');

  js := TJs.Create;

  result := TJsonObject.Create;
  result.EmitCompact := False;

  //  Call Eval to add the function to the context's global object
  success := js.Eval(sbScript,result);
  if (success = False) then
    begin
      //  Examine the result for an exception.
      WriteLn(result.Emit());

      //  Also examine the LastErrorText.
      WriteLn(js.LastErrorText);
      Exit;
    end;

  //  ------------------------------------------------------------------------------
  //  Call the function describeCar(car)

  funcCall := TJsonObject.Create;
  funcCall.EmitCompact := False;

  //  Create JSON specifying the function name and arguments
  //  In this case, there is only 1 argument, and it is an object.

  //  {
  //    "name": "describeCar",
  //    "args": [
  //      {
  //        "make": "Toyota",
  //        "model": "Corolla",
  //        "year": 2022
  //      }
  //    ]
  //  }

  funcCall.UpdateString('name','describeCar');

  //  Create the JSON object that is the argument.
  arg := TJsonObject.Create;
  arg.UpdateString('make','Toyota');
  arg.UpdateString('model','Corolla');
  arg.UpdateInt('year',2022);

  //  Create the arguments array.
  argsArray := TJsonArray.Create;
  argsArray.AddObjectCopyAt(0,arg);

  //  Add the "args" array to the funcCall.
  funcCall.AppendArrayCopy('args',argsArray);

  WriteLn(funcCall.Emit());

  success := js.CallFunction(funcCall,result);
  if (success = False) then
    begin
      //  Examine the result for an exception.
      WriteLn(result.Emit());

      //  Also examine the LastErrorText.
      WriteLn(js.LastErrorText);
      Exit;
    end;

  WriteLn(result.Emit());

  //  The describeCar JavaScript function returns nothing. 
  //  Therefore, the result is "undefined".

  //  {
  //    "type": "undefined",
  //    "value": "undefined"
  //  }

  //  However, the function emitted text to the console.

  sbOut := TStringBuilder.Create;
  js.ConsoleOutputSb(sbOut);
  WriteLn(sbOut.GetAsString());

  //  Output:
  //  This is a 2022 Toyota Corolla.

  //  -----------------------------------------------------------
  //  Note: If the object argument is simple, this is an alternative
  //  and simpler way of creating the funcCall:

  funcCall.Clear();
  funcCall.UpdateString('name','describeCar');
  funcCall.UpdateString('args[0].make','Toyota');
  funcCall.UpdateString('args[0].model','Corolla');
  funcCall.UpdateInt('args[0].year',2022);
  WriteLn(funcCall.Emit());


  sbScript.Free;
  js.Free;
  result.Free;
  funcCall.Free;
  arg.Free;
  argsArray.Free;
  sbOut.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.