## 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.