Project Euler - Even Fibonacci numbers

sumOfEvenFibonacciNumbers.js

function *fibbonacciGenerator(max) {
  if (!max) {
    console.log("Please enter a maximum number for the fibbonacciGenerator");
    return;
  }
  var previous = 0;
  var next = 1;
  var current = 1;
  while (current < max) {
    yield current;
    current = previous + next;
    previous = next;
    next = current;
  }
}

function sumEvenValues(sum, numToAdd) {
  if (numToAdd % 2 !== 0) {
    return sum;
  }
  return sum + numToAdd;
}

var sum = 0;
for (var i of fibbonacciGenerator(4E9)) {
  sum = sumEvenValues(sum, i)
}
console.log(sum);