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uniqWith()

uniqWith<T>(array, comparator): T[]

Creates a duplicate-free version of an array using a comparator function.

note

First occurrence wins when duplicates are found.

Type Parameters​

T: T​

The type of elements in the array.

Parameters​

array: readonly T[]​

The array to inspect.

comparator: (a, b) => boolean​

The function invoked to compare elements.

Returns: T[]​

A new array with unique elements.

Since​

2.0.0

Performance​

O(n²) — custom comparators cannot leverage Set optimization.

Example​

const objects = [{ x: 1, y: 2 }, { x: 2, y: 1 }, { x: 1, y: 2 }];

uniqWith(objects, (a, b) => a.x === b.x && a.y === b.y);
// => [{ x: 1, y: 2 }, { x: 2, y: 1 }]

How it works?​

Removes duplicates using a custom comparator function. First occurrence wins.

Use Cases​

Deduplicate with custom equality 📌​

Remove duplicates using a custom comparison function. Perfect for complex objects or fuzzy matching.

const products = [
  { name: "Laptop", price: 999.99 },
  { name: "LAPTOP", price: 999.99 },
  { name: "Phone", price: 699 },
];

const unique = uniqWith(
  products,
  (a, b) => a.name.toLowerCase() === b.name.toLowerCase() && a.price === b.price
);
// => [Laptop, Phone]

Remove near-duplicates with tolerance​

Deduplicate numeric values within a tolerance range. Useful for sensor data, measurements, or approximate matching.

const readings = [10.01, 10.02, 20.0, 10.03, 30.0];

const unique = uniqWith(readings, (a, b) => Math.abs(a - b) < 0.1);
// => [10.01, 20.0, 30.0]

Deep equality deduplication​

Remove duplicates based on deep object comparison. Essential for complex nested structures.

const configs = [
  { settings: { theme: "dark", lang: "en" } },
  { settings: { theme: "dark", lang: "en" } },
  { settings: { theme: "light", lang: "fr" } },
];

const unique = uniqWith(
  configs,
  (a, b) => JSON.stringify(a.settings) === JSON.stringify(b.settings)
);
// => [dark/en, light/fr]