filter

collection

Iterates over elements of collection, returning an array of all elements predicate returns truthy for.

Installation

Import

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

Source Code

Implementation

/**
 * Iterates over elements of collection, returning an array of all elements predicate returns truthy for.
 *
 * @param collection - The collection to iterate over.
 * @param predicate - The function invoked per iteration.
 * @returns Returns the new filtered array.
 *
 * @example
 * ```ts
 * const users = [
 *   { 'user': 'barney', 'active': true },
 *   { 'user': 'fred', 'active': false }
 * ];
 * filter(users, (o) => !o.active); // [{ 'user': 'fred', 'active': false }]
 * ```
 */
export function filter<T>(
  collection: readonly T[] | Record<string, T>,
  predicate: (
    value: T,
    index: number | string,
    collection: readonly T[] | Record<string, T>
  ) => boolean
): T[] {
  const result: T[] = [];

  if (Array.isArray(collection)) {
    for (let i = 0; i < collection.length; i++) {
      if (predicate(collection[i], i, collection)) {
        result.push(collection[i]);
      }
    }
  } else {
    const record = collection as Record<string, T>;
    for (const key in record) {
      if (Object.prototype.hasOwnProperty.call(record, key)) {
        if (predicate(record[key], key, record)) {
          result.push(record[key]);
        }
      }
    }
  }

  return result;
}

Example

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

const users = [
{ 'user': 'barney', 'active': true },
{ 'user': 'fred', 'active': false }
];
filter(users, (o) => !o.active); // [{ 'user': 'fred', 'active': false }]

Related Functions

countBy

Creates an object composed of keys generated from the results of running each element of collection thru iteratee. The corresponding value of each key is the number of times the key was returned by iteratee.

each

Iterates over elements of collection and invokes iteratee for each element. The iteratee is invoked with three arguments: (value, index|key, collection).

eachRight

This method is like each except that it iterates over elements of collection from right to left.

every

Checks if predicate returns truthy for all elements of collection.

find

Iterates over elements of collection, returning the first element predicate returns truthy for.

findLast

This method is like find except that it iterates over elements of collection from right to left.