Creating an increment function: Why is my code not working?

Keywords´╝Ü javascript function increment

Question: 

I am following a course and I had to solve the following challenge: Creating a function that, everytime it is run, adds a number to an array, like this:

 [1]
 [1,2]
 [1,2,3} etc...

I have exactly the same code ad the instructor on my snippets, but for the instructor works perfectly while for me it does not (Console shows "Undefined" which does makes sense because I defined all I needed at the beggining, before the function.

I tried tweaking the code because I actually thought there might be a mistake in my instructor's code, since she didn't "re-define" the variable as of in

count = count++; 

besides tweaking the code in many ways, I don't seem to know what else to try. I am pretty new to javascript, also.

var output = [];
var count = 1;

function fizzBuzz() {
  output.push(count);
  count++;
  console.log(output);
}

No error messages, just "Undefined" in the console.

Answers: