Arrays.previous()

added in 0.0.1 • last revisions

Syntax

function previous<T>(array: readonly T[], fromIndex: number): T | undefined

Gets the previous element in the array, starting at the given index.

Parameters
`array`	An array with any number of elements.
`fromIndex`	An in-bounds index. The function will return the element belonging to `fromIndex - 1`, or `array.length - 1` if `fromIndex` is `0`.

Example

import { Arrays } from 'potence';

const array = [3, 1, 5];

console.log(Arrays.previous(array, 0));   // -> 5
console.log(Arrays.previous(array, 2));   // -> 1

Remarks

This function will “wrap”, that is it will return the last element if the passed index belongs to the first element in the array.

The index must be within the bounds of the array. If it isn’t, the function returns undefined. In TypeScript, you can use the non-null assertion operator (!) on the return value if you are absolutely certain the index is in-bounds.

This function is analogous to Arrays.next().