My five cents:
Both direction array of integers function.
When range(0, 5) become [0, 1, 2, 3, 4, 5].
And range(5, 0) become [5, 4, 3, 2, 1, 0].
Based on this answer.
function range(start, end) {
const isReverse = (start > end);
const targetLength = isReverse ? (start - end) + 1 : (end - start ) + 1;
const arr = new Array(targetLength);
const b = Array.apply(null, arr);
const result = b.map((discard, n) => {
return (isReverse) ? n + end : n + start;
});
return (isReverse) ? result.reverse() : result;
}
P.S. For use in real life you should also check args for isFinite() and isNaN().