Function deduplicate

Package: @litert/utils-arraySource: packages/partials/array/src/Functions/Deduplicate.ts

Removes duplicate values from an array and returns a new array without duplicates. For basic types (strings, numbers, etc.), deduplication uses strict equality (===) by default. For complex/object types, a makeKey function must be provided to map each element to a comparable value, unless the references are known to be unique already (pass null expressly to opt into reference equality).

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Import

import { deduplicate } from '@litert/utils-array';

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Signature

// Overload 1 — for basic types (optional makeKey)
function deduplicate<T extends IBasicType>(
    items: readonly T[],
    makeKey?: (v: T) => any
): T[];

// Overload 2 — for complex/object types (makeKey required; pass null for reference equality)
function deduplicate<T extends IAdvancedType>(
    items: readonly T[],
    makeKey: null | ((v: T) => any)
): T[];

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Parameters

Parameter	Type	Description
items	readonly T[]	The array to deduplicate
makeKey	((v: T) => any) | null	Maps each element to a comparable key. Omit for basic types (uses ===). Pass null to use reference equality for complex types

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Return Value

A new array containing only the unique elements in their original order.

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Examples

import { deduplicate } from '@litert/utils-array';

// Basic types — no makeKey needed
console.log(deduplicate([1, 2, 2, 3, 1]));      // [1, 2, 3]
console.log(deduplicate(['a', 'b', 'a']));       // ['a', 'b']

// Object types — provide makeKey
const users = [{ id: 1, name: 'Alice' }, { id: 2, name: 'Bob' }, { id: 1, name: 'Alice' }];
console.log(deduplicate(users, u => u.id));      // [{ id: 1, ... }, { id: 2, ... }]

// Reference equality for objects (pass null)
const obj = { x: 1 };
console.log(deduplicate([obj, obj, { x: 1 }], null)); // [{ x: 1 }, { x: 1 }]