Name: Anjana Vakil.関数型JSのための不変データ構造｜JSConf EU (Anjana Vakil: Immutable data structures for functional JS | JSConf EU)
Uploaded: 2021-01-14T08:34:09.000Z
Duration: 26 min 33 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

You can find me on Twitter at my name and today I'd like to talk to you about immutable

data structures for functional programming in JavaScript.

We're going to take a look at what immutable data structures are, why they're a really

cool way to handle the immutability that we typically use when we're doing functional

programming and how we can do that in JavaScript because I hear y'all like JavaScript!

I'm probably the only not-web-developer in the room.

I work with them to develop a custom query language for data in the scientific research

I'm also an alum of the Recurse Center, which is a fantastic programming community in New

York City, and I am an alum of the Outreach Program, which if you have haven't heard of

it, it's getting women and more folks involved in these by giving them internships at Mozilla.

So I'm really happy to chat about those things if you want to come grab me after the talk.

But you might know that I like functional programming.

Anybody else agree with me that functional programming is cool?

Yeah, so functional programming is a pretty great way to avoid some of the headaches of

like imperative and object-oriented programming.

In functional programming, what we typically do is conceive of our programs as being just

That means their transform their inputs to outputs, and that's all they do.

They don't have my side effects like changing things in the console, and my taking things

But our data becomes data in, data out, and transformers of data.

And one thing that goes hand-in-hand with this, with avoiding side effects is immutable

Immutable data meaning once we've created it, it never changes.

So this is a really good way of changing something accidental outside of your function.

If everything is immutable, you can't change anything.

So immutability another thing that rocks and it rocks pretty hard for other reasons that

But speaking of rocks, let's talk about rocks.

So this is a rock, and immutability rocks in the way that rocks rock.

Now I don't know about you, but I've been going to a lot of tech conferences recently

and I've been feeling like there has enough poetry.

So I'd like to read you a poem: Nobody sits like this rock sits.

This is from -- Don't thank me, thank I Heart Huckabees, that's

So this is really how immutable data rocks.

Once we've created it, it never changes and that's amazing because it can help us avoid

So with immutability, we have some things pretty easy, but other things become harder

So let's say I have an array called foo and it's got some numbers in it.

Let's say I have a zoo with some animals -- more fun!

And I decided that I want to change something up about my zoo.

Maybe I want to replace that rabbit there with something a little more exotic.

I'm happy because I wanted a more exotic zoo.

I didn't have to change anything except for that one little cell in my array.

That's pretty sweet but my co-worker over was expecting zoo to be filled with earth

beings, earth animals, and wasn't accounting for there being an alien in it.

We have to manage who's been changing what, when -- who's been putting which animals in

We have to have a lot of overhead to manage that state, and that gives us headaches as

We also get bugs in the code because maybe I was only planning -- or my co-worker was

only planning -- to handle terrestrial beings and didn't have a case of aliens being accounted

So these are some side effects of immutability that don't make us happy.

Let's try doing things the immutable way.

So in an immutable world, my array, my zoo, once I've created it, it just sits and is

What I can do if I want a new zoo that's more exotic is I can make a copy that's the same

size as my original array, and I can make the modification I want, so I can put my alien

And so this is pretty sweet because now my co-worker is maybe, and they're, like, whoo,

nothing broke in my program, and it's all still animal creatures but I had to copy over

I had to allocate the space for that entire array, even all of the stuff that didn't change.

So this means that my code runs pretty slow.

The complexity on those things are bad because copying is a waste of both time and space.

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Anjana Vakil.関数型JSのための不変データ構造｜JSConf EU (Anjana Vakil: Immutable data structures for functional JS | JSConf EU)

mindset

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arbitrary

structure