Best way to test if an element doesnt exist

https://support.smartbear.com/testcomplete/docs/app-objects/common-tasks/waiting-process-or-window-activation.html#WaitMethods

Wait for the button or other object to show up and continue depending on the results of the Wait method.

Hi, there is a few possible options:

1) WaitWindow

var p = Sys.Process("app");

Indicator.PushText('Checking object...');
var obj = p.WaitWindow("propValue", "Value", -1, 1000);
Indicator.Clear();

if(obj .Visible)
    obj.Click();

2) Aliases

Aliases.app.obj1.RefreshMappingInfo();
var activeObject = Aliases.app.obj1.FindAllChildren("propName", "*");

if(aqObject.GetProperties(activeObject ).Count != 0)
    return true;
else
    return false;

3) Exist

var p = Sys.Process("Impuls");
var obj= p.WaitWindow("propName", "propValue", -1, 1000);
if(obj.Exists == true) {
     obj.Find("propName", 'propValue', [treeValue]).Click();
}

4) Wait for element until it's exist

function waitUntil(obj, licznik) {
  var licznik = licznik || 60;
  for (var i = 1; i <= licznik; i++) {
    if (obj.Exists == true) {
      aqUtils.Delay(1000);
    } else {
      break;
    }
  }
}

Hi and thanks for the replies but how would wait or exist work ? Remember these are two different test cases. It should never be visible in Test case 2 so would it not fail as an element not found ?

I will read up on Aliases and explore that route.