DEV Community

Cover image for Is Javascript Object.groupBy() worth the hype? let's find out

Is Javascript Object.groupBy() worth the hype? let's find out

Max Svidlo on December 16, 2023

With the upcoming release of NodeJS 21, we're getting an exciting new method that should make our object groupings more straightforward: Object.gro...
Read full post
Collapse
 
lnahrf profile image
Lev N. •

I mean, I’ve been using maps in JS for years. groupBy is a convenience.

Collapse
 
svidlak profile image
Max Svidlo •

Well, now it's also a performance increase and not just syntactic sugar, which makes it even better

Collapse
 
lnahrf profile image
Lev N. •

No doubt, but it’s nothing new.

Collapse
 
lionelrowe profile image
lionel-rowe •

I don't think there's any "hype" about Object.groupBy being super performant. It's just a convenience method. If it happens to be slightly more performant for some datasets, that's great, but I wouldn't rely on any performance gains being stable between different engines, different versions of the same engine, different hardware, or even necessarily different runs on the exact same setup.

The key advantage is that it gives better ergonomics. Wanting to split an array into groups is a pretty common use case that didn't have an ergonomic way of doing it before now. For example, if you had a list of users that you wanted to group into admin and non-admin users, you either had to initialize variables for both then iterate with a for loop (a bit messy and verbose, especially with the array initialization in TypeScript), or you had to iterate through the array twice with Array#filter (wasteful as you only really wanted 1 iteration). Now it's simple:

Object.groupBy(users, (user) => user.role === 'admin' ? 'admin' : 'non-admin')
Enter fullscreen mode Exit fullscreen mode

It's also pretty versatile — e.g. you can use it to segment an array into groups of a given size:

const GROUP_SIZE = 42
const arr = new Array(100)

Object.values(Object.groupBy(arr, (_, i) => Math.floor(i / GROUP_SIZE)))
// [Array(42), Array(42), Array(16)]
Enter fullscreen mode Exit fullscreen mode
Collapse
 
citronbrick profile image
CitronBrick •

Actually, I needed this method this week & came upon this article, & discovered groupBy.

Collapse
 
manchicken profile image
Mike Stemle •

Showing performance graphs without posting the code makes them hard to understand.

Collapse
 
svidlak profile image
Max Svidlo •

I got you covered @manchicken
github.com/svidlak/groupby-benchmark

Collapse
 
manchicken profile image
Mike Stemle •

Thanks! It’s always good to post the code with these things. Well-done.

Thread Thread
 
svidlak profile image
Max Svidlo •

My first article ever written so mistakes are unavoidable

Thread Thread
 
manchicken profile image
Mike Stemle •

No doubt. My advice: learn to love your mistakes.

Collapse
 
efpage profile image
Eckehard •

We should also ask, if it´s worth to blow up the language core to infinitiy, just to add some convenience functions (see also this post). I would love this feature (if I ever used it), if it was part of a library. But too many features may also be confusing.

Collapse
 
svidlak profile image
Max Svidlo •

Well, every language has to go thru some kind of an evolution sometimes in order to improve itself, whenever its via internal optimization or via introduction of new API's
(the same as ES6 introduced us some functionalities to replace lodash / rambda dependencies, fatArrow functions),

Its important for JavaScript to keep on evolving and improving as the whole client-side ecosystem of JavaScript is evolving nonstop, so the language has to support those new needs.

Collapse
 
nevodavid profile image
Nevo David •

I use it with lodash