compact

1/**
2 * Removes elements from an array that do not pass the predicate function.
3 * If no predicate is provided, removes all falsy values.
4 *
5 * @param arr - The array to filter.
6 * @param predicate - Optional custom predicate function.
7 * @returns A new filtered array.
8 */
9export function compact<T>(arr: T[], predicate: (value: T) => boolean = Boolean): T[] {
10  return arr.filter(predicate);
11}

• Flexible predicate support

  Allows filtering based on a custom predicate, enabling a wide range of use cases beyond just removing falsy values.

• Default behavior matches Lodash-style compact

  When no predicate is provided, it removes all falsy values (false, 0, '', null, undefined, NaN) — a common utility in data cleanup.

• Non-mutating

  Returns a new array, leaving the original untouched, which supports functional programming best practices.

• Short and performant

  Leverages native .filter() for efficient execution with minimal overhead.

• Readable and concise

  Simple signature and intuitive behavior make it easy to adopt in any codebase.

Tests | Examples

1test('compact removes default falsy values', () => {
2  expect(compact([0, 1, false, 2, '', 3])).toEqual([1, 2, 3]);
3  expect(compact(['a', '', 'b', null, 'c'])).toEqual(['a', 'b', 'c']);
4});
5
6test('compact with custom predicate', () => {
7  expect(compact([1, 2, 3, 4, 5], n => n > 2)).toEqual([3, 4, 5]);
8  expect(compact(['cat', 'dog', ''], str => str.length > 0)).toEqual(['cat', 'dog']);
9  expect(compact([{ ok: true }, { ok: false }], item => item.ok)).toEqual([{ ok: true }]);
10});

Common Use Cases

• Cleaning user input or form data

  Remove empty strings, null, or undefined values from user-submitted arrays.

• Filtering optional values

  Eliminate placeholder values from datasets (e.g., [1, '', 2, null] → [1, 2]).

• Custom filtering

  Use with a predicate like (x) => x > 0 or (x) => typeof x === 'string' for domain-specific cleanup.

• React or UI rendering

  Clean up arrays before rendering to avoid passing invalid or empty content into components.

• Preparing data for export or APIs

  Filter out unnecessary or incomplete records before sending data to a server or displaying in a report.