Delphi ActiveX

Call a JavaScript Function Returning an Integer

See more JavaScript Examples

Demonstrates how to call a JavaScript function that returns an integer. Delphi ActiveX

var
success: Integer;
sbScript: TChilkatStringBuilder;
js: TChilkatJs;
result: TChilkatJsonObject;
funcCall: TChilkatJsonObject;
retval: Integer;

begin
success := 0;

//  ----------------------------------------------------------------------------------
//  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 := TChilkatStringBuilder.Create(Self);
success := sbScript.LoadFile('js_call_function.js','utf-8');
if (success = 0) then
  begin
    Memo1.Lines.Add(sbScript.LastErrorText);
    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 := TChilkatJs.Create(Self);

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

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

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

//  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 := TChilkatJsonObject.Create(Self);

//  Create JSON defining the function call:

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

funcCall.UpdateString('name','calculateScore');
funcCall.UpdateString('args[0]','Player1');
funcCall.UpdateInt('args[1]',10);
funcCall.UpdateInt('args[2]',20);

funcCall.EmitCompact := 0;
Memo1.Lines.Add(funcCall.Emit());

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

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

JavaScript

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