Is Sum Even

isSumEven

Given nums, an array of integers, return true if the sum of all elements is an even number or false if not.

isSumEven( [1, 2, 3, 4, 5] ) => false
isSumEven( [1, 1, 2, 2] ) => true
isSumEven( [ ] ) => true

Note: We'll consider an empty array to have an even sum because the sum of all elements is 0.