onclick is deprecated?

'KeyboardEvent.keyIdentifier' is deprecated and will be removed in M53, around September 2016. See https://www.chromestatus.com/features/5316065118650368 for more details.

So I got the above error for the code that I was instructed to write for the "returning values" section of the object oriented javascript course, except for "onclick." I then took somebody's advice and used

button.addEventListener('click', function() = { var result = dice.roll(); printNumber(result); });

and I got the far above error message. Am I doing something wrong or are times just a' changin'? And if the convention is changing, how would I then perform this task?

Thanks guys, Jack