Array Functions

A collection of utility functions for working with arrays.

chunk

Splits an array into chunks of the specified size.

Usage

const array = [1, 2, 3, 4, 5, 6, 7, 8];
const chunked = chunk(array, 3);
console.log(chunked); // [[1, 2, 3], [4, 5, 6], [7, 8]]

Code

/**
 * Splits an array into chunks of the specified size
 * @param array - The array to chunk
 * @param size - The size of each chunk
 * @returns An array of chunks
 */
function chunk<T>(array: T[], size: number): T[][] {
  if (!array.length || size <= 0) {
    return [];
  }

  const chunks: T[][] = [];
  for (let i = 0; i < array.length; i += size) {
    chunks.push(array.slice(i, i + size));
  }

  return chunks;
}

uniq

Removes duplicate values from an array.

Usage

const array = [1, 2, 2, 3, 4, 4, 5];
const uniqueValues = uniq(array);
console.log(uniqueValues); // [1, 2, 3, 4, 5]

Code

/**
 * Removes duplicate values from an array
 * @param array - The array to process
 * @returns A new array with unique values
 */
function uniq<T>(array: T[]): T[] {
  return [...new Set(array)];
}

uniqBy

Removes duplicate values from an array based on a computed key.

Usage

const array = [
  { id: 1, name: 'John' },
  { id: 2, name: 'Jane' },
  { id: 1, name: 'John (duplicate)' }
];

// Creating a unique list based on the id property
const uniqueById = uniqBy(array, item => item.id);
console.log(uniqueById);
// [{ id: 1, name: 'John' }, { id: 2, name: 'Jane' }]

// For simple values, you can use a mapping function
const numbers = [1.1, 2.5, 1.9, 2.1];
const uniqueByFloor = uniqBy(numbers, Math.floor);
console.log(uniqueByFloor); // [1.1, 2.5]

Code

/**
 * Removes duplicate values from an array based on a key function
 * @param array - The array to process
 * @param iteratee - Function invoked per element to generate the criterion for uniqueness
 * @returns A new array with unique values determined by the iteratee
 */
function uniqBy<T, K>(array: T[], iteratee: (item: T) => K): T[] {
  const seen = new Map<K, boolean>();
  return array.filter(item => {
    const key = iteratee(item);
    if (seen.has(key)) {
      return false;
    }
    seen.set(key, true);
    return true;
  });
}

groupBy

Groups array items based on a key function.

Usage

const people = [
  { name: 'John', age: 25 },
  { name: 'Jane', age: 30 },
  { name: 'Jack', age: 25 }
];

const grouped = groupBy(people, person => person.age);
console.log(grouped);
// {
//   '25': [{ name: 'John', age: 25 }, { name: 'Jack', age: 25 }],
//   '30': [{ name: 'Jane', age: 30 }]
// }

Code

/**
 * Groups array items based on a key function
 * @param array - The array to group
 * @param keyFn - Function that returns the grouping key for an item
 * @returns An object with keys from keyFn and values as arrays of matching items
 */
function groupBy<T, K extends string | number | symbol>(
  array: T[],
  keyFn: (item: T) => K
): Record<K, T[]> {
  return array.reduce((result, item) => {
    const key = keyFn(item);
    if (!result[key]) {
      result[key] = [];
    }
    result[key].push(item);
    return result;
  }, {} as Record<K, T[]>);
}

head

Gets the first element of an array.

Usage

const array = [1, 2, 3, 4, 5];
const first = head(array);
console.log(first); // 1

const emptyArray = [];
const emptyResult = head(emptyArray);
console.log(emptyResult); // undefined

Code

/**
 * Gets the first element of an array
 * @param array - The array to query
 * @returns The first element of the array, or undefined if the array is empty
 */
function head<T>(array: T[]): T | undefined {
  return array[0];
}

last

Gets the last element of an array.

Usage

const array = [1, 2, 3, 4, 5];
const lastElement = last(array);
console.log(lastElement); // 5

const emptyArray = [];
const emptyResult = last(emptyArray);
console.log(emptyResult); // undefined

Code

/**
 * Gets the last element of an array
 * @param array - The array to query
 * @returns The last element of the array, or undefined if the array is empty
 */
function last<T>(array: T[]): T | undefined {
  return array.length ? array[array.length - 1] : undefined;
}