chunk-arr

A collection of utility functions to split an array into chunks by size or certain condition.

Why?

• Minimal APIs
• Written in TypeScript
• Actively maintained
• Fully coverage tests
• Inspired from Ruby chunk

Install

$ npm install chunk-arr

Usage

const { chunkBy } = require('chunk-arr');

chunkBy([3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5], n => n % 2);
// [ [3, 1], [4], [1, 5, 9], [2, 6], [5, 3, 5] ]

API

chunk(array, [size = 1])

Like lodash/chunk, split the array into chunks of size. If array can not be split evenly, the final chunk will be the remaining elements.

array

• Require: true
• Type: any[]

The array to process

size

• Require: false
• Type: number
• Default: 1

The size of each chunk. Return empty array if size smaller than 1.

Note: The size will be converted to the largest number that smaller than size by Math.floor.

Example:

const { chunk } = require('chunk-arr');
// or
// const chunk = require('chunk-arr');

const chars = ['a', 'b', 'c', 'd', 'e'];

console.log(chunk(chars));
// Output: [ ['a'], ['b'], ['c'], ['d'], ['e'] ]

console.log(chunk(chars, 2.4));
// Output: [ ['a', 'b'], ['c', 'd'], ['e'] ]

chunkBy(array, func)

Iterate over array elements, chunking them together based on the return value of the block.

Consecutive elements which return the same block value are chunked together.

array

• Require: true
• Type: T[]

The array to process

func

• Require: true
• Type: (element: T, index: number): U

The function used to chunk array based on its return value. It takes two arguments: the current element is iterating and its index

Example: Split based on element types

const { chunkBy } = require('chunk-arr');

const arr = [true, -3, 1, 'a', 'b', 'c'];

console.log(chunkBy(arr, e => typeof e));
// Output: [ [true], [-3, 1], ['a', 'b', 'c'] ]

chunkWhile(array, func)

This method splits the array between previous and current element if the function receives those elements return false.

array

• Require: true
• Type: Array<T>

The array to process

func

• Require: true
• Type: (previous: T, current: T): boolean

The function, which receives the previous and current element, uses to split array between them if it returns false

Example:

• Split array into non-decreasing chunks

const { chunkWhile } = require('chunk-arr');

const nums = [0, 9, 2, 2, 3, 2, 7, 5, 9, 5];

console.log(chunkWhile(nums, (prev, curr) => prev <= curr));
// Output: [[0, 9], [2, 2, 3], [2, 7], [5, 9], [5]]

• Convert increasing numbers into the compact string

const { chunkWhile } = require('chunk-arr');

const nums = [1, 2, 4, 9, 10, 11, 12, 15, 16, 19, 20, 21];

console.log(chunkWhile(nums, (prev, curr) => prev + 1 === curr)
            .map((chunk) => chunk.length > 2 ? `${chunk[0]}-${chunk[chunk.length - 1]}` : chunk)
            .join(',')
);
// Output: '1,2,4,9-12,15,16,19-21'

• Split Markdown file by sections

const Fs = require('fs');
const { chunkWhile } = require('chunk-arr');

try {
    const data = Fs.readFileSync('./README.md', 'utf8');
    console.log(chunkWhile(data.split('\n'), (_, current) => !current.startsWith('#')));
} catch (error) {
    console.error(error);
}

// Output:
// [
//   ['# chunk-arr', ...],
//   ['## Why?, ...],
//   ...
//   ['## Author', ...]
// ]

Author

• Nam Hoang Le

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