reduceRight

collection

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

Installation

Import

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

Source Code

Implementation

/**
 * This method is like reduce except that it iterates over elements of collection from right to left.
 *
 * @param collection - The collection to iterate over.
 * @param iteratee - The function invoked per iteration.
 * @param accumulator - The initial value.
 * @returns Returns the accumulated value.
 *
 * @example
 * ```ts
 * const array = [[0, 1], [2, 3], [4, 5]];
 * reduceRight(array, (flattened, other) => flattened.concat(other), []); // [4, 5, 2, 3, 0, 1]
 * ```
 */
export function reduceRight<T, TResult>(
  collection: readonly T[] | Record<string, T>,
  iteratee: (
    accumulator: TResult,
    value: T,
    index: number | string,
    collection: readonly T[] | Record<string, T>
  ) => TResult,
  accumulator: TResult
): TResult {
  if (Array.isArray(collection)) {
    for (let i = collection.length - 1; i >= 0; i--) {
      accumulator = iteratee(accumulator, collection[i], i, collection);
    }
  } else {
    const record = collection as Record<string, T>;
    const keys = Object.keys(record).reverse();
    for (const key of keys) {
      accumulator = iteratee(accumulator, record[key], key, record);
    }
  }

  return accumulator;
}

Example

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

const array = [[0, 1], [2, 3], [4, 5]];
reduceRight(array, (flattened, other) => flattened.concat(other), []); // [4, 5, 2, 3, 0, 1]

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.

filter

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

find

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