Fizzbuzz: Test your Flow control skills in Javascript

fizzBuzz = function(num) {
  // write a function that receives a number as its argument;
  // if the number is divisible by 3, the function should return 'fizz';
  // if the number is divisible by 5, the function should return 'buzz';
  // if the number is divisible by 3 and 5, the function should return
  // 'fizzbuzz';
  //
  // otherwise the function should return the number, or false if no number
  // was provided or the value provided is not a number
}