sortedIndex (Lodash compatibility)

Implement binary search directly

This sortedIndex function operates with complexity due to handling null, undefined, and various type support.

Instead, implement a faster, more modern binary search directly or use a dedicated library.

Finds the lowest index at which a value should be inserted into a sorted array.

const index = sortedIndex(array, value);

Reference

sortedIndex(array, value)

Use sortedIndex to find the position to insert a value in a sorted array. It uses binary search to find the position quickly.

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

// Find insertion position in number array
sortedIndex([30, 50], 40);
// Returns 1 (40 is positioned between 30 and 50)

// Find insertion position in string array
sortedIndex(['a', 'c'], 'b');
// Returns 1 ('b' is positioned between 'a' and 'c')

// When the same value exists, returns the first position
sortedIndex([1, 2, 2, 3], 2);
// Returns 1 (position of the first 2)

For null or undefined arrays, returns 0.

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

sortedIndex(null, 1); // 0
sortedIndex(undefined, 1); // 0

Parameters

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

Returns

(number): Returns the lowest index to insert the value. If the array is null or undefined, returns 0.