30-seconds-of-code/snippets/js/s/initialize-array-with-reversed-range.md

title, type, language, tags, cover, excerpt, dateModified

title	type	language	tags	cover	excerpt	dateModified
Initialize array with reversed range	snippet	javascript	array	interior-4	Initializes an inclusive array with numbers in a range, reversed, using a common `step` difference.	2020-10-20T23:02:01+03:00

Initializes an array containing the numbers in the specified range (in reverse) where start and end are inclusive with their common difference step.

• Use Array.from() to create an array of the desired length, (end - start + 1) / step.
• Use Array.prototype.map() to fill the array with the desired values in the given range.
• Omit the second argument, start, to use a default value of 0.
• Omit the last argument, step, to use a default value of 1.

const initializeArrayWithRangeRight = (end, start = 0, step = 1) =>
  Array.from({ length: Math.ceil((end + 1 - start) / step) }).map(
    (v, i, arr) => (arr.length - i - 1) * step + start
  );

initializeArrayWithRangeRight(5); // [5, 4, 3, 2, 1, 0]
initializeArrayWithRangeRight(7, 3); // [7, 6, 5, 4, 3]
initializeArrayWithRangeRight(9, 0, 2); // [8, 6, 4, 2, 0]