(Delphi DLL) Call a JavaScript Function Returning an Integer

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Note: This example requires Chilkat v11.4.0 or greater.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
sbScript: HCkStringBuilder;
js: HCkJs;
result: HCkJsonObject;
funcCall: HCkJsonObject;
retval: Integer;

begin
success := False;

// ----------------------------------------------------------------------------------
// The Javascript function called in this example is shown at the bottom of this page.
// -----------------------------------------------------------------------------------

// In this example, we'll load the Javascript function definition from a file.
// It doesn't need to come from a file.  It could just as easily be loaded from a string.
sbScript := CkStringBuilder_Create();
success := CkStringBuilder_LoadFile(sbScript,'js_call_function.js','utf-8');
if (success = False) then
  begin
    Memo1.Lines.Add(CkStringBuilder__lastErrorText(sbScript));
    Exit;
  end;

// Note: Each instance of a Chilkat Js object automatically establishes
// its own internal runtime and context.  Applications do not need to explicitly create
// the JavaScript runtime or context.
js := CkJs_Create();

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

// Call Eval to add the function (shown at the bottom of this page) 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;

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

// The expected output is "undefined":

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

//    When Eval processes a script containing only a function declaration,
//    it successfully performs the action (the function becomes defined).
//    However, since the script consists of a statement that produces no value,
//    the script's overall completion value is empty. In JavaScript, the
//    absence of a value is represented by `undefined`.
// 
//    Therefore, the Eval call returns `undefined`.

// ------------------------------------------------------------------------------
// Call the function calculateScore("Player1", 10, 20)

funcCall := CkJsonObject_Create();

// Create JSON defining the function call:

// {
//   "name": "calculateScore",
//   "args": [ "Player1", 10, 20 ]
// }

CkJsonObject_UpdateString(funcCall,'name','calculateScore');
CkJsonObject_UpdateString(funcCall,'args[0]','Player1');
CkJsonObject_UpdateInt(funcCall,'args[1]',10);
CkJsonObject_UpdateInt(funcCall,'args[2]',20);

CkJsonObject_putEmitCompact(funcCall,False);
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));

// Output:

// {
//   "type": "int",
//   "value": 37
// }

retval := CkJsonObject_IntOf(result,'value');
Memo1.Lines.Add('retval = ' + IntToStr(retval));

CkStringBuilder_Dispose(sbScript);
CkJs_Dispose(js);
CkJsonObject_Dispose(result);
CkJsonObject_Dispose(funcCall);

end;

function calculateScore(name, pointsA, pointsB) {
    // Return length of name + both scores
    return name.length + pointsA + pointsB;
    }