Chunking an array in JavaScript

Recently I was working with some data coming out of a Redis pipeline and I
wanted to take the data and split it up into an array of X items per key. I was
working with PHP, this wouldn’t have been a big deal, just use array_chunk and
get on with my day.

With JavaScript though, there’s no such function.

There are definitely options though. In fact, there are 46 packages out on npm
at the time of this writing that appear to handle splitting / chunking an array.

While these options are completely viable, it seemed like overkill to me to
introduce a new dependency just to handle something as trivial as creating an
array from an array one time in my codebase.

The thing is, the concept of chunking isn’t anything complex. Start with an
array and transform it into another array. Could handle it a handful of
different ways, as well.

Here’s the quick and dirty that I went with to get the job done. For the sake of
the blog post, the first line is generating an array with 100 numerical items:

const unchunked = Array.apply(null, { length: 100 }).map(, Number
const unchunkedLength = unchunked.length
const chunked = 
const chunkSize = 3

for (let i = 0 i < unchunkedLength i += chunkSize) {
  chunked.push(unchunked.slice(i, i + chunkSize

console.log(unchunked, chunked

But I mean, if you would rather add an additional dependency to your codebase,
by all means, don’t let me stop you 😉

Josh Sherman - The Man, The Myth, The Avatar

About Josh

Husband. Father. Pug dad. Musician. Founder of Holiday API, Head of Engineering and Emoji Specialist at Mailshake, and author of the best damn Lorem Ipsum Library for PHP.

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