function recursiveMultiply(a, b) {
  if(!b) return 0;
  return a + recursiveMultiply(a, b-1);
}
8.5 Recursive Multiply: Write a recursive function to multiply two positive integers without using the * operator (or / operator). You can use addition, subtraction, and bit shifting, but you should minimize the number of those operations.

O(b), BUT there is a better solution that could do O(log Math.min(a, b))

@param a
@param b
@returns {*}