Const type parameters are so powerful

WOOHOO, I cant wait to bother my bossman to upgrade to version 5

typescript getting f**cking complex

Hey Matt, thank you for a great video! I appreciate your effort. Today I just stumbled upon a use case for that feature, and I cannot wrap my head around solving it with the existing approaches. Given:

type Column = {
name: string;
}

type Template<C extends Column = Column> = {
sortBy: Template['schema'][number]['name'];
schema: C[];
}

const template: Template = {
sortBy: 'help',
schema: [{name: 'hello'}, {name: 'there'}],
}

is there any way to make it complain about the passed value to sortingColumnName and allow only 'hello' | 'there'?

Any help would be greatly appreciated!

Ok, so I really don't want to get beat up here. But I work with TS and other langs day-to-day. What's the big benefit of this? I get the "feeling" its about "Intellisense". True | False?

Extremely helpful. Thanks

Typescript is bureaucracy .

I'm at a loss for words. great. thank you

I thought I knew typescript because I know how to use "interface"

Now I feel like I don't know it at all.

It this point, I'm surprised MS hasn't just made a C# to JavaScript transpiler....

We can still have a working "makeRoles" function in the current typescript version by sprinkling some "readonly" and "as const". So is "const T" just some syntactic sugar?

Hey Matt,

I have a question

Is there any way to write a mongo query which can be typed .

I tried FilterQuery but it accepts any value which is not in the interface

So weird, I was struggling with a LocalStorage implementation that uses Generics last night and this perfectly solves the problem. Thanks!

Great video! New to the channel, subbed

Seems like a nice improvement! Any idea why the extra 'const' keyword is necessary in the generic since you're defining the object 'as const' already?

Could you not just `return T as const`

Do you have a super secret version of the playground? As I can't get 'insider' only 'nightly' ?

This is so awesome

I always use Jimi Hendrix as a mock name on my drafts lol

finally, Narrow trick is not reliable at times. This feature is great, you can infer as const and then remap type omitting "readonly" recursively. This is same as Narrow but more stable

Any idea why it defaults to erasing most of the inferred type information in the first place?? 🤷‍♂️

I am getting error while using this in typescritpt playground
I selected nigly build but I get error like this

function something<const T>(data: T) {
return data
}

Variable 'T' implicitly has an 'any' type.(7005)

This EXACT issue has been the bane of my existence. I cannot even begin to describe how many times I've googled something akin to "infer generic as const."

Before you had to write
function a<T>(...tuple: readonly [...T]) {}
const is much more clean and idiomatic

i fucking love TypeScript, playing around with the genius typing system is fun

Your TypeScript course is already out?

I don't like polluting TypeScript with more gobbidy goop cos it makes things less readable

Thanks, Matt! Just purchased your Total Typescript course today :)

It’s taken too long

I wish this feature were available now, would've saved me a lot of grief XD

Great video, thanks.

Is there any other language with a type system more insane than Typescript's?

Homie Matt cranking out those videos. You love to see it. Low key learn something from everyone.

Stuff's great. I didn't know about either technique, so making toy libraries for myself I just had to remember to <const> my own objects I pass into functions, definitely not something you'd want to force your users to do :)

amazing feature!

I just want one feature: i)structural pattern matching

Great stuff as always. Thanks for the update!

This is so cool

I just needed this exact feature yesterday for the first time, what a coincidence.
I wish the same thing happened to all features I felt the need for...

I'd it possible to get that code example shown in the TS playground?

The flags when you pass admin has canCreatePost as optional and undefined, surely it shouldn't exist because it doesn't exist in the flags object for an admin?

Maya nimo opawa oi biliba

I can't wait for v5 to drop.

WoW TS is more and more versatile, my only concern is will it's performance improvement would catch up with these changes thou or the server will still clanky as before

Another TS frustration gone.
Now I just need to get rid of all the hacks from my code that previously made this possible.

Niceee

first