### Challenge: MaxIndex Implement a function **`maxIndex`** that takes in a vector of numbers and returns the index of the highest number in it. If the vector is empty, the function should return **`-1`**. ```=json maxIndex([1, 2, 3]); // Returns 2 maxIndex([3, 2, 1]); // Returns 0 maxIndex([1, 3, 2, 3]); // Returns 1 maxIndex([]); // Returns -1 ```