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Illustrated Notes

Immer's Immutable Data, Gifting Socks, and Personal Assistant Bots

Published or updated on October 10, 2019

Today we're going to look at immutable data. With socks. And personal assistant bots.

A robot and a pair of socks

I know, you're already so excited.

Immutability and state are two developer buzzwords it took me forever to "get."

Their underlying meanings aren't necessarily that complex.
But it's tough to fully comprehend what they mean, and why they're important, until you see them in action.

State just means the way an application is at a single point in time.

For example, if we've typed "how does CSS grid work" into the search bar, and there are three checkboxes ticked, and we have a dropdown menu open that's the current "state" of things.
If we close the menu that's a state change.

Behind the scenes in apps we have to account for every state an app could be in (which gets expontential very quicky). This is usually called "managing state" and appears to be a neverending problem.

Immutable State is one approach to solving our complex state problem – it simply means making a second copy of things before you change them.

It's the same as copying and pasting a new document before liberally changing enourmous chunks of it. Then when you realise your poor editing choices and want to go back to the original version, it's there waiting for you.

Writing immutable code is a wildly popular concept in general. And a good idea when you don't want to muck everything up.

Okay now you're all caught up on the jargon, lets get to some illustrated notes!

These are from a course Michel Weststrate made about their elegant new tool Immer – it helps handle manage immutable state in a sane way.

The course is up as a free community resource on egghead, and is aptly named Immutable JavaScript Data Structures with Immer

Course illustation of a set of rubik's cubes changing state

Despite my allegic intolerance towards thinking about state and immutability, this course turned out to be a delight.

Michel walks us through building a gifting app with React & Immer that seamlessly handles all the messy state work.

immer 1

Visually drawing out how all the functions and drafts and edits fit together was essential for this one. I wouldn't have grokked it otherwise.

immer 2

immer 3

CSS is awesome cup

Yes the cup in the illustration is based on this classic CSS one that I don't own, but kind of want to.

If you're currently allergic to state & immutability as well, it might be the time to re-test your tolerances and see if Immer can help cure it.

The Whole Illustrated Note

the full immer illustrated note

Want to learn more?

A high-res & printable version of the notes, plus the full course is avaliable here on the Immutable JavaScript Data Structures with Immer page.