Success is Not Defined

I was writing a JS script interacting with an API. Last one had "success" as a response attribute (with true/false values). I forgot that it's a key, so I called "success" as a variable. When I ran the script it returned nothing, but an error: "success is not defined". That was the smartest statement I have ever recieved from a terminal. As for me it's almost true, I have no idea how to define success, it's something so temporary.