int a[17]; size_t n = sizeof(a)/sizeof(a[0]);
Array.from(Array(10).keys()) //=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
[...Array(10).keys()] //=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]