Is 2019 the year of TypeScript?

This comment in the Jest repository, https://github.com/facebook/jest/pull/7554#issuecomment-454358729, has been floating around on the Twitterverse the past few days and seems to be garnering a lot of attention.

The fact that a Facebook project is migrating to TypeScript (TS) is kind of big deal considering they're also behind Flow, a direct competitor of TS.

Other prominent JS devs have been chiming in as well. Some with a little more cursing, so apologies in advance. 😉

Is this the final nail in the coffin for Flow? Is it another year where TypeScript adoption continues to rise and it becomes the Year of TypeScript?

There's even a horse_ts Twitter account now. It's not too hard to guess who it is, but I still find it pretty funny.

"So if you’ve been a holdout (like me, to be honest), 2019 is definitely the year to learn TypeScript.", @kball quote from https://zendev.com/2019/01/15/frontend-development-topics-to-learn-in-2019.html

Share your thoughts in the comments below and feel free to shamelessly plug your TS posts, if you've written any on dev.to. I'll shamelessly plug first.

Consider Using TypeScript

Nick Taylor ・ Oct 8 '17

#typescript

Photo by NordWood Themes on Unsplash

Comments

[Ferdy Budhidharma]

I'm one of the maintainers for React's types, and I'm writing a post series on how TypeScript works with JSX. Hopefully this'll clear up some of the magic smoke behind how JSX typing works :)
dev.to/ferdaber/typescript-and-jsx...

[Ben Halpern]

Cool!

[Sebastian Vargr]

I really hope not..

Typescript, has its usecases, but without native support it is almost pointless to me.
Too much setup.

The easier debugging is nice however.

My main gripe is problably that it tends to promote large corp style OOP with bajillions of pointless interfaces and classes.

Which in my experience leads to state soup and lack of code-mutability.

[Nick Taylor]

For sure it can promote large corp style OOP. Perhaps, and I have no data for this, just my musings, is that Angular promoted this once they adopted TypeScript. DI, classes, decorators etc...

I've been using TypeScript in React and browser extensions and almost never use OOP. The only time I've really used classes in React was for components that required state. Aside from that rarely, and now that hooks are stable and able, function components would be the way to go for new work.

Having said that, OOP is not a bad thing. Just like anything, people can do bad things 😉

[Sebastian Vargr]

I am mostly against OOP, for a number of reasons that would longwinded and off topic. :)

I my world, the TS gains do not outweigh the layers of complexity added to all parts of the developing process from developer skills to the libraries and build systems we use today.

It is unnecessary for most things, so why bother with it?

[Sean G. Wright]

I don't think Typescript does anything more OOP than JavaScript (ES2015+) does, besides Interfaces (which also appear in functional languages).

Typescript supports all the same functional concepts that JavaScript does, including being able to type higher-order functions. It also includes other functional concepts that aren't in JavaScript, like union types, or even better, discriminated unions.

[Sebastian Vargr]

I am talking about complexity, and the way I see the language generally used in practice.

TS has more features, that is the entire point of the language.

Exampletime,
Just yesterday I was debugging a TS npm library, all I wanted was add to poke the source with a few console logs.

But because it was a TS library it came in 5 different ES versions, had a slew of typings I had to see through, and the actual source was not included because npm is for JS.

This would have forced me to get the source code, hook it up to my npm dependencies and then build it with my few debug changes.

Is there a better way to debug, problably yes, I could have explored the map in the browser and addd breakpoints, or use some other tool.

Had this been a JS library I would have spend a few minutes looking over the source.

Now, imagine a junior wanting to do this.

Complexity comes at cost, it is the entire point of functional programming, but centered around the problem of state management.

Toting TS as a good tool for functional programming is like saying eating children is a good way to prevent hunger.

It overlooks the actual problem.

[Sean G. Wright]

Yeah, that all makes sense. It's definitely a different workflow.

I'm used to other languages that don't ship source code in packages, so this is nothing new to me.

Npm package authors could include source if they wanted - so the lack of it seems more like a personal choice on the part of the author.

Also, the issues you noted about all the transpiled variations of JavaScript for that Typescript authored lib ... those appear with JavaScript libraries too!

If a js lib author uses Babel to support older versions of Node or browsers, they will include transpiled versions of their js code.

This seems to be more an issue of the JavaScript tooling ecosystem still needing to mature.

In .NET/C# I can make a package that has compiled code only, but includes a hash to a git commit. When I'm debugging, my IDE pulls the repo code down to my machine and lets me debug into it live. It's a great developer experience.

I think the JavaScript community will come up with similar creative solutions.

[Sebastian Vargr]

Lack of tools is not really the problem, quite the opposite the way I see it.

Tools should make us more productive, not be a nessesary thing to be productive at all.

The fact that we are even talking about solving the problem with more IDE tools suggests a flaw in the system.

We need something that will reduce complexity at this point. Otherwise the frontend community will end up fragmenting into completely unessesary domains of knowledge based on frameworks and what kind of transpilation we do.

More so than it already has.

[Nick Taylor]

Came across this today. I rarely use classes myself, but I thought this was pertinent to the convo.

Evan You

@youyuxi

Ironically I think TypeScript has helped me more with avoiding classes than using them. Vue 3 is a 100% TS codebase with 0 usage of classes.

15:34 PM - 21 Sep 2019

53 408

[Sean G. Wright]

And I love the new VueJs 3 functional component API RFC.

Functional + Types = 💗.

[Ben Calder]

I tend to agree. I have to use it at work and I understand the arguments in favour; but to me it still feels like a ball-and-chain compared to vanilla JS. I do understand some of the benefits; but there are also some downsides:

• junior devs coming from type-safe languages can get a false sense of security: e.g. not doing proper type-checking on data coming from a back-end
• assuming that private really means private
• not getting a proper understanding of JS. ((synctatic) sugar is bad for you)

But yes - mainly my problem is that it can encourage a classic OOP approach to coding when IMO one of the big strengths of JS is that it facilitates some really effective functional approaches.

[Ben Halpern]

Might as well call it hypescript at this point. It seems like it’s all the rage.

Probably a good sign that an all-the-rage thing in JavaScript is a tool that should fundamentally help write more sound software across the board, and one that’s been around long enough to become pretty stable I’d imagine.

[Stephen Chiang]

Hmmm HypeScript could have some fun typings in that language...

const newVariable: ohYeahStrings!;
const anotherVariable: awesomeNumber![];
const thirdVariable: bestObjectEver!{};

export everyoneIsInterestedInThisClass someClassName {};
export mostInterfaceableInterface IinterfaceName {};

I dig it!

[Sdu]

I like HypeScript already 🙆 TAKE ALL MY MONEY!!

[Martin Arista]

I do believe it's all the rage right now but there are times when I see the value in a JS implementation. I still think there is not enough support for certain types and you are left either writing your own adding any to describe something. And in converse, when working on a large codebase or teams the comfort of types is very helpful.

And naturally a shameless plug for a react-native expo starter I made to solve that problem for RN.
github.com/mrtnrst/expo-typescript...

[Stephen Chiang]

I'm curious as to what types you're missing as well.

I have not encountered that yet. An interesting quirk is that if you only need Type checking then you should make an interface. Interfaces are thrown out at compile time which leaves your code lighter. Classes are kept and should only be used if you actually need to instantiate an instance of that type during runtime.

[Totiimon]

Which are some types you think are not supported? I was interested in jumping in this TS-hype-train and things like this are good to know before :)

[Sean G. Wright]

I get the feeling Martin meant 3rd party libraries that don't have typings defined (if written in JavaScript) or are written in Typescript but don't provide their own robust types for APIs.

This can definitely happen, though it's a lot less common (and painful) than it was 3-4 years ago.

I recently used an Angular-specific 3rd party library for authentication. They didn't include types for some of their underlying JavaScript code.

I had the option of either using :any as the type (or leaving the type off, as it will default to :any) or writing my own types to describe their JavaScript APIs.

I wrote out some type definitions that covered the part of their APIs that I was using and the definitions took about 15 minutes after looking at the JavaScript code in the package under /node_modules.

If you decide to use :any (or, again, leave off any type annotations, which works fine) you are where you would be with plain JavaScript - so nothing lost.

If you add type annotations, you gain all the benefits of types - my favorite being discoverability of APIs.

[Totiimon]

Right, It made more sense after reading more about it. I think the discoverability in general is such a nice thing you get by going with static types that is almost worth it by that alone haha

[Sean G. Wright]

Another nice thing about Typescript is how the types "flow" through the application.

Often I only need to annotate a couple of parameters, variables, methods.

Then when using those things the rest of my code is able to infer the results of operations.

For example:

function getName() {
  return 'lalo';
}

const name = getName();

Notice, there are 0 type annotations here...

But, Typescript knows that name is a string and anywhere I use name, either as a parameter or in an assignment or expression, Typescript will flow that string type to the next place I'm working with name.

A lot of developers when first using Typescript will add a ton of annotations to their code, only to realize later that Typescript is great at inferring type information and doesn't need us to be so explicit.

[Vignesh D]

Typescript seems to be really gathering attention nowadays. I remember avoiding Angular, as I had to learn another language.. Typescript. But its that same typescript that made me take Angular as well as trying all Possibilities to use wherever I use javascript from React to Electron Js. High quality intellisense and type enforcement makes Typescript 1st class.

[Nick Taylor]

If you're in Reactland, it couldn't be easier to get started with TypeScript these days since support landed in Babel 7 and they implemented support in Create React App.

npx create-react-app your-project-name --typescript

[Sophie The Lionhart]

To be fair having to learn Typescript AND Angular at the same time makes learning both significantly more difficult.

[Jesse M. Holmes]

That was my exact course, and I believe that is why I am so biased toward TypeScript. I avoided so much JavaScript pain.

I definitely took courses on fundamental JS later on, because as wonderful as TS is, at some point you will break your face if you don’t understand the underlying language.

[Sophie The Lionhart]

Oh yeah I LOVE TS, I just was overwhelmed with it at my first shot(I come from static typed languages but was very familiar with JS by this point), and it was annoying not knowing if my problems were TS or Angular when I tried learning both at the same time.

[Vignesh D]

Been There. Done that. 👍

[Vignesh D]

Nope. I stayed with React and Typescript. Angular's strategy felt too heavy for simple applications.

[Sophie The Lionhart]

I wasn't defending angular, I don't use it either. I was saying that learning both at the same time makes both hard to learn.

[Sebastian Vargr]

JavaScript is supported with no setup for almost all libraries, and run native in the browser.

Anything that adds complexity to that situation i would deem as a bad solution.

With TS, we are just shifting the work to someplace else and adding new problems for people to learn rather than solving the original issues.

[Justin Lam]

Not exactly sure what it means that 2019 is the year of TypeScript. I worked on large projects at Microsoft and they used TypeScript exclusively on large scale systems for years. And there is a good reason it was used over vanilla JavaScript. I can't imagine not having type safety beyond 1 developer.

[Nick Taylor]

All I mean is, maybe this is the year that its adoption really skyrockets. I've been using it since 2015 and it's 🔥.

[Sung M. Kim]

I've just started dabbling with TypeScript and..
A simple change helped me to reduce the file size today 😉
probably because I wasn't doing Babel right 😅

But it wasn't so bad so more reason to like/move/try to use TypeScript 👍

[Nick Taylor]

I know a lot of people came to TypeScript from Angular 2 and on, but for me it was a different path.

We adopted TypeScript in 2015 where I was working at the time and used it with a custom front-end library. After that, I jumped into the world of FinTech with React and TypeScript. And since then all my professional React experience has been pretty much all in TypeScript. And aside from React, I've used it in node as well. Works really well there too.

It plays really well with React. You know the TS team cares about Reactland, because they added the fragment syntax fairly quickly. And it plays well with Preact too. It was a minor fix, but I had a PR go into Preact for a types issue just over a year ago. Felt pretty good about that.

[Sean G. Wright]

I think one of the wonderful things about Typescript is that it's an opt-in type system.

You can take the following JavaScript file (app.js):

const names = ['lawrence', 'kim', 'koala'];

const shortNames = names.filter(n => n.length <= 4);

And copy it into a Typescript file (app.ts):

const names = ['lawrence', 'kim', 'koala'];

const shortNames = names.filter(n => n.length <= 4);

And then compiled it with the Typescript compiler:

tsc app.ts

No changes were need to my JavaScript!

If I wanted to I could add just 1 type:

const names = ['lawrence', 'kim', 'koala'];

const shortNames: string[] = names.filter(n => n.length <= 4);

And everything still works!

---

Sure, Typescript code that you might see in an Angular application can have types everywhere and a bunch of strict compiler flags - but this is one side of the spectrum.

Typescript is happy and helpful anywhere along that spectrum.

Use :any (or don't add an annotation at all - it's the same thing), leave the compiler options loose, and ease yourself into it.

Then as the project grows in complexity, start flipping on compiler flags, add more types and see where your expectations of your code don't match reality.

---

If you just prefer no type information in your code, cool! Don't use Typescript :)

(JavaScript still has types, it's just weakly typed and doesn't require you to specify them)

But it's not an all or nothing thing - approach Typescript on your own terms and I think you'll find it enjoyable and interesting.