Delphi DLL

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. Delphi DLL

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Js, StringBuilder, JsonArray, JsonObject;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
sbScript: HCkStringBuilder;
js: HCkJs;
result: HCkJsonObject;
funcCall: HCkJsonObject;
arg: HCkJsonObject;
argsArray: HCkJsonArray;
sbOut: HCkStringBuilder;

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 := CkStringBuilder_Create();
CkStringBuilder_Append(sbScript,'function describeCar(car) { console.log(`This is a ${car.year} ${car.make} ${car.model}.`); }');

js := CkJs_Create();

result := CkJsonObject_Create();
CkJsonObject_putEmitCompact(result,False);

// Call Eval to add the function to the context's global object
success := CkJs_Eval(js,sbScript,result);
if (success = False) then
  begin
    // Examine the result for an exception.
    Memo1.Lines.Add(CkJsonObject__emit(result));

    // Also examine the LastErrorText.
    Memo1.Lines.Add(CkJs__lastErrorText(js));
    Exit;
  end;

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

funcCall := CkJsonObject_Create();
CkJsonObject_putEmitCompact(funcCall,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
//     }
//   ]
// }

CkJsonObject_UpdateString(funcCall,'name','describeCar');

// Create the JSON object that is the argument.
arg := CkJsonObject_Create();
CkJsonObject_UpdateString(arg,'make','Toyota');
CkJsonObject_UpdateString(arg,'model','Corolla');
CkJsonObject_UpdateInt(arg,'year',2022);

// Create the arguments array.
argsArray := CkJsonArray_Create();
CkJsonArray_AddObjectCopyAt(argsArray,0,arg);

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

Memo1.Lines.Add(CkJsonObject__emit(funcCall));

success := CkJs_CallFunction(js,funcCall,result);
if (success = False) then
  begin
    // Examine the result for an exception.
    Memo1.Lines.Add(CkJsonObject__emit(result));

    // Also examine the LastErrorText.
    Memo1.Lines.Add(CkJs__lastErrorText(js));
    Exit;
  end;

Memo1.Lines.Add(CkJsonObject__emit(result));

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

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

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

sbOut := CkStringBuilder_Create();
CkJs_ConsoleOutputSb(js,sbOut);
Memo1.Lines.Add(CkStringBuilder__getAsString(sbOut));

// 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:

CkJsonObject_Clear(funcCall);
CkJsonObject_UpdateString(funcCall,'name','describeCar');
CkJsonObject_UpdateString(funcCall,'args[0].make','Toyota');
CkJsonObject_UpdateString(funcCall,'args[0].model','Corolla');
CkJsonObject_UpdateInt(funcCall,'args[0].year',2022);
Memo1.Lines.Add(CkJsonObject__emit(funcCall));

CkStringBuilder_Dispose(sbScript);
CkJs_Dispose(js);
CkJsonObject_Dispose(result);
CkJsonObject_Dispose(funcCall);
CkJsonObject_Dispose(arg);
CkJsonArray_Dispose(argsArray);
CkStringBuilder_Dispose(sbOut);

end;