I was wondering, can you create a function with an optional parameter.

Example:

```
function parameterTest(test)
{
   if exists(test)
   {
     alert('the parameter exists...');
   }
   else
   {
     alert('The parameter doesn\'t exist...');
   }
}

```

So if you call `parameterTest()` then the result would be a message "The parameter doesn't exist...". And if you call `parameterTest(true)` then it would return "the parameter exists...". 

Is this possible?