why could a check if (document.addEventListener) returns false

Question

On what basis does a check if (document.addEventListener) return false? Is there a way we can change this?

Answer 1

If this code snippet returns false, this means that the addEventListener method property is not support by the browser. This is the case for Internet Explorer, where attachEvent is used instead:

if (document.addEventListener){  
  document.addEventListener(...);
} else if (document.attachEvent){  
  document.attachEvent(...);  
}

Answer 2

if (document.addEventListener) evaluates to false if there's no addEventListener method in document. This check is usually done to see if you can use this method to attach event to DOM element (works in most browsers except IE).

is there a way we can change this ?
This question I don't completely understand. Probably, you want something like document.attachEvent('onload', callback); for IE. You can't really add addEventListener method to document (well, maybe you can, but it wouldn't make sense).

Docs for addEventListener