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

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());

JavaScript

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