(Delphi ActiveX) Call a JavaScript Function Returning a String

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

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

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Integer;
sbScript: TChilkatStringBuilder;
js: TChilkatJs;
result: TChilkatJsonObject;
funcCall: TChilkatJsonObject;
retval: WideString;

begin
success := 0;

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

// function greet(name) {
//     return "Hello, " + name + "!";
// }

sbScript := TChilkatStringBuilder.Create(Self);
sbScript.Append('function greet(name) { return "Hello, " + name + "!"; }');

js := TChilkatJs.Create(Self);

result := TChilkatJsonObject.Create(Self);
result.EmitCompact := 0;

// Call Eval to add the function to the context's global object
success := js.Eval(sbScript.ControlInterface,result.ControlInterface);
if (success = 0) then
  begin
    // Examine the result for an exception.
    Memo1.Lines.Add(result.Emit());

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

// ------------------------------------------------------------------------------
// Call the function greet("Michael")

funcCall := TChilkatJsonObject.Create(Self);

// Create JSON specifying the function name and arguments

// {
//   "name": "greet",
//   "args": [ "Michael" ]
// }

funcCall.UpdateString('name','greet');
funcCall.UpdateString('args[0]','Michael');

success := js.CallFunction(funcCall.ControlInterface,result.ControlInterface);
if (success = 0) then
  begin
    // Examine the result for an exception.
    Memo1.Lines.Add(result.Emit());

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

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

// Output:
// {
//   "type": "string",
//   "value": "Hello, Michael!"
// }

retval := result.StringOf('value');
Memo1.Lines.Add(retval);

// Output:
// Hello, Michael!
end;