Ideas for JavaScript helpers

helpers.js

const range = (end, start) => {
  // Return an Array of a sequence of integers from start to end-1.
  // Let end be an non-negative integer, which represent the last number in a sequence exclusively.
  // Let start be an (optional) integer (zero, negative or positive), which represents the first number in a sequence inclusively.
  // Examples:
  // range(4) produces [0, 1, 2, 3]
  // range(4, -3) produces [-3, -2, -1, 0, 1, 2, 3]
  if (end === undefined) return [];
  if (end < 0) return [];
  return Array(end - (start ?? 0))
    .fill()
    .map((_, index) => start + index);
};