Delphi ActiveX

Prevent JavaScript Infinite Loops

See more JavaScript Examples

Demonstrates how prevent infinite loops or prevent the JavaScript from running for a longer amount of time than allowed. Delphi ActiveX

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;

begin
success := 0;

// This is the JavaScript we'll run:

// console.log('Starting infinite loop...'); while(true) {};

sbScript := TChilkatStringBuilder.Create(Self);
sbScript.Append('console.log(''Starting infinite loop...''); while(true) {};');

js := TChilkatJs.Create(Self);

// Set a limit on the amount of time (in seconds) the script is allowed to run.
// If the JavaScript takes longer than this amount of time, then Chilkat kills the script without crashing the host program.
// The default value of TimeoutSeconds is 0, which indicates no limit.
// For this example, set a limit of 2 seconds.
js.TimeoutSeconds := 2;

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

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

    // The result contains this:

    // 	{
    // 	  "exception": {
    // 	    "message": "interrupted - JavaScript exceeded the Chilkat.Js.TimeoutSeconds",
    // 	    "stack": [
    // 	      {
    // 	        "func": "<eval>",
    // 	        "file": "<input>",
    // 	        "line": 1,
    // 	        "col": 8
    // 	      }
    // 	    ]
    // 	  }
    // 	}

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

// We should never get here..
Memo1.Lines.Add('Succeeded.');
Memo1.Lines.Add(result.Emit());
end;