unionBy

arrays

This method is like union except that it accepts iteratee which is invoked for each element of each arrays to generate the criterion by which uniqueness is computed.

Try in Playground

Installation

Import

import { unionBy } from '@tulx/utils';

Source Code

Implementation

/**
 * This method is like union except that it accepts iteratee which is invoked for each element
 * of each arrays to generate the criterion by which uniqueness is computed.
 *
 * @param arrays - The arrays to inspect.
 * @param iteratee - The iteratee invoked per element.
 * @returns The new array of combined values.
 *
 * @example
 * ```ts
 * unionBy([2.1], [1.2, 2.3], Math.floor); // [2.1, 1.2]
 * ```
 */
export function unionBy<T>(...args: readonly unknown[]): T[] {
  if (args.length < 2) {
    return [];
  }

  const iteratee = args[args.length - 1] as ((value: T) => unknown) | string;
  const arrays = args.slice(0, -1) as readonly T[][];

  const getValue =
    typeof iteratee === 'string'
      ? (item: T) => (item as Record<string, unknown>)[iteratee]
      : iteratee;

  const result: T[] = [];
  const seen = new Set<unknown>();

  for (const array of arrays) {
    for (const value of array) {
      const key = getValue(value);
      if (!seen.has(key)) {
        seen.add(key);
        result.push(value);
      }
    }
  }

  return result;
}

Example

import { unionBy } from '@tulx/utils';

unionBy([2.1], [1.2, 2.3], Math.floor); // [2.1, 1.2]

Related Functions

chunk

Creates an array of elements split into groups the length of size. If array can't be split evenly, the final chunk will be the remaining elements.

compact

Creates an array with all falsy values removed. The values false, null, 0, "", undefined, and NaN are falsy.

concat

Creates a new array concatenating array with any additional arrays and/or values.

difference

Creates an array of array values not included in the other given arrays. The order and references of result values are determined by the first array.

differenceBy

This method is like difference except that it accepts iteratee which is invoked for each element of array and values to generate the criterion by which they're compared.

differenceWith

This method is like difference except that it accepts comparator which is invoked to compare elements of array to values.