"TypeError: Document not active" or "TypeError: The expression cannot be converted to return the specified type." Javascript Fullscreen API Error Messages:

Error message 

 

In a recent Firefox (64.0) you'll see this error:

TypeError: The expression cannot be converted to return the specified type.

in Chrome (71.0.x):

TypeError: Document not active

Cause

 

A rather meaningless and unhelpful error message occurs when one tries to exit fullscreen via javascript if the document isn't actually in fullscreen mode.

Solution

The solution is to check whether we are currently in fullscreen mode.

Snippet

Run it in jsfiddle, for testing the fullscreen mode.

See also

 

https://developer.mozilla.org/en-US/docs/Web/API/Element/requestFullScreen
https://developer.mozilla.org/en-US/docs/Web/API/DocumentOrShadowRoot/fullscreenElement