Delphi DLL

Call a JavaScript Function Returning a String

See more JavaScript Examples

Demonstrates how to call a JavaScript function that returns a string. 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, JsonObject;

...

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

begin
success := False;

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

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

sbScript := CkStringBuilder_Create();
CkStringBuilder_Append(sbScript,'function greet(name) { return "Hello, " + name + "!"; }');

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 greet("Michael")

funcCall := CkJsonObject_Create();

// Create JSON specifying the function name and arguments

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

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

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": "string",
//   "value": "Hello, Michael!"
// }

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

// Output:
// Hello, Michael!

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

end;