javascript - Why does document.createEvent("Event") intermittently error with "Object Expected" in IE 11? -

I'm testing some units that create artificial incidents. Indicates that I should be able to:

  document.createEvent ("Event");  

When I run the unit test, sometimes they are successful, and the second time they fail on the createEvent call with the "object object" error. Running that code in the console also results in incompatible results. I will reload the page, or open a new tab, and the function will work, the next time I try, it fails with the error.

I betrayed the link in the link by Windows 10 for something, as happened above, with that person - do not let this happen.

Any idea why sometimes a single call works and is throwing errors a second time?