I’d be like “Oh boy let me get redirected to lots of useful answers to my question next time too”.

I don’t understand why you would frame that as being “slapped”. Does having your question marked as a duplicate hurt your feelings?

Isn’t it a good thing if your question is marked as a duplicate? That means you now have lots of answers readily available which already answered the question.

In Javascript you can do let a = undefined, defining the variale a as undefined.

A significant difference to defining it as null is that typeof null == "object", while typeof undefined == "undefined".