sortedLastIndexOf (Lodash compatibility)

::: warning Implement binary search directly

This sortedLastIndexOf function operates slowly due to complex binary search handling and type validation.

Instead, implement faster, more modern binary search directly or use Array.prototype.lastIndexOf().

:::

Finds the index where a value last appears in a sorted array.

const index = sortedLastIndexOf(array, value);

Usage

sortedLastIndexOf(array, value)

Use sortedLastIndexOf to find the index where a specific value last appears in a sorted array. It uses binary search to find the value quickly.

import { sortedLastIndexOf } from 'es-toolkit/compat';

// Find value in number array
sortedLastIndexOf([1, 2, 3, 4, 5], 3);
// Returns 2

// When value doesn't exist
sortedLastIndexOf([1, 2, 3, 4, 5], 6);
// Returns -1

// When duplicate values exist, returns the last index
sortedLastIndexOf([1, 2, 2, 3, 3, 3, 4], 3);
// Returns 5 (position of the last 3)

// 0 and -0 are treated as equal
sortedLastIndexOf([-0, 0], 0);
// Returns 1

Empty arrays, null, or undefined return -1.

import { sortedLastIndexOf } from 'es-toolkit/compat';

sortedLastIndexOf([], 1); // -1
sortedLastIndexOf(null, 1); // -1
sortedLastIndexOf(undefined, 1); // -1

Parameters

• array (ArrayLike<T> | null | undefined): The sorted array. Using an unsorted array can produce incorrect results.
• value (T): The value to find.

Returns

(number): Returns the index where the value last appears. If the value doesn't exist, returns -1.