array uniques

uniques.test.ts

import { uniques, uniquesByAtt } from './uniques';


describe('uniques function', () => {
	it('should filter unique elements by strict equality by default', () => {
		const value = [1, 2, 3, 3, 2, 1, 4, 5, 5];
		const res = uniques(value);
		expect(res).toEqual([1, 2, 3, 4, 5]);
	});

	it('should filter unique elements using comparator function', () => {
		const value = [{ a: 3 }, { a: 2 }, { a: 5 }, { a: 2 }];
		const res = uniquesByAtt(value, 'a');
		expect(res).toEqual([{ a: 3 }, { a: 2 }, { a: 5 }]);
	});
});

uniques.ts

export function uniques(array: any[], comp: (a: any, b: any) => boolean = (a, b) => a === b) {
	const len = array.length, res = new Array(len);
	let c = 0;

	function fresh(value: any) {
		for (let j = 0; j < c; j++) {
			if (comp(value, res[j])) {
				return false;
			}
		}
		return true;
	}

	for (let i = 0; i < len; i++) {
		if (fresh(array[i])) {
			res[c++] = array[i];
		}
	}

	res.length = c;
	return res;
}

export function uniquesByAtt<K extends string>(array: Array<{ [k in K]: any }>, att: K) {
	return uniques(array, (a, b) => a[att] === b[att]);
}