TypeScript "as const" assertion is 🔥🔥🔥

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Typescript "as const" assertion is 🔥
Javascript const is not really defining a constant, but Typescript's "as const" assertion fixes this for JS.
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[@bballer3010]

Kinda a new dev, I’ve been doing development for websites for about a year and a half now. Never had a senior developer. Thank you so much for answering these small questions that don’t appear to be a big deal, until they are. Much love for stumbling on this channel and hope it grows to help developers everywhere.

[@DaveGrayTeachesCode]

Glad I could help!

[@0xtz_]

I'm working on a project and the senior is using Typescript so I need to use it too and maaan it's amazing no bugs pain etc u fix all in the editor ... Now no vanilla JavaScript in big projects 👌🏼

[@DaveGrayTeachesCode]

Excellent!

[@emmanueltech9705]

Dave on his way to 100k subs you deserve more man 💯

[@DaveGrayTeachesCode]

Thank you!

[@abdulazeez.98]

Excellent tip!

[@Its.all.goodman]

That's interesting, never thought this before because Im currently learning typescript. Im subscribing for more content like this

[@DaveGrayTeachesCode]

Glad it was helpful!

[@starlines07]

Cool info 👍

[@jampy42]

This is really cool, thanks!

[@DaveGrayTeachesCode]

Welcome!

[@thebowshock7729]

Hey Dave, there are also cases such as these: type Fruit = "Orange" | "Apple" const myVariable: Fruit = "Orange" I have noticed there are cases when TS doesn't like that const value and treats it as a nondescript string, but doing _as const_ seems to lock it down: const myVariable: Fruit = "Orange" as const

[@DaveGrayTeachesCode]

Right on!

[@undefined_object]

There are object.freeze and seize methods to make the objects real const

[@DiegoBM]

You left it in a cliff-hanger! Good move! Hehe

[@mikamanelka1326]

haha, perfect. needed this today

[@DaveGrayTeachesCode]

Right on! 🤘

[@jasondotjson34]

Yeah, but I like to use object as constants like this: const obj:object = {message:"hello"}; I cannot override variable but i can override properties. So it's kind of constant cuz it cannot be re-assignment. But yeah it's kinda cool operator to be honest.

[@olteanumihai1245]

its equivalent with final

[@catbb]

🙏

[@supportic]

Object.freeze(obj) in JS. You're welcome

[@DaveGrayTeachesCode]

Already knew about that. The same functionality but not self-documenting like TypeScript.

[@sney2002]

Are nested objects also constant?

[@DaveGrayTeachesCode]

Yes, try it out. Typescript will flag it even layers deep.

[@sayonara3465]

But what the useful from that? In js when i getten a result from database or form etc, how i can push it to array const, and yeah i want the array as const not let or var coz i don’t want to change the name of variable, so again i don’t understand what the point or useful from this?

[@DaveGrayTeachesCode]

This is a concept from functional programming to understand that is also applied to libraries/frameworks like React - Do not "mutate" (aka modify) the original state, but instead, create a new object, array, etc.

[@efari]

const *in JS* doesn't mean "constant value" it means "constant assignment"

[@DaveGrayTeachesCode]

This video explains that "const" in JS is not actually a "constant" as others may think about from other programming languages - so we're probably in agreement here. What does constant mean in programming languages? "In computer programming, a constant is a value that should not be altered by the program during normal execution, i.e., the value is constant." Reference: en.wikipedia.org/wiki/Constant_(computer_programming)

[@efari]

@@DaveGrayTeachesCode yea i meant "const in JS doesn't mean..." i was indeed agreeing with you, but expanding the explanation :)

[@scroogemcduckenjoyer]

Interesting, why they named that tho?

[@DaveGrayTeachesCode]

JS has some weird parts. Using const does "constantly" refer to the same memory pointer for objects.. but the weird part compared to most languages is that the inner properties (or elements if an array) can still be changed. TS provides a way to curb that behavior with the "as const" assertion.

[@PeidosFTW]

It's the same behaviour for the final keyword in java. Declaring an arraylist as final will still allow you to change the contents, pretty standard behaviour for many common languages

[@Alex-bc3xe]

my old trick

[@ScriptRaccoon]

This is not entirely correct. 1) TypeScript won't prevent constants from being reassigned in runtime. It "only" gives you a warning in development. 2) There is a JavaScript method to achieve this: Object.freeze(). This prevents reassignment also in runtime.

[@DaveGrayTeachesCode]

Given more than the 60 seconds of a short, I can give a deeper discussion. That said, you are basically saying "If you use Typescript, but choose to ignore it..." and while true, I didn't think I needed to say that. You can say the same for anything TS does as all Javascript is valid when you ignore the TS warnings.

[@WesleyDuSellone]

Great! const as const

[@simply-dash]

all that does is add Object.freeze?

[@DaveGrayTeachesCode]

Typescript adds type safety. You need to heed the warnings it provides. If you do not want to use TS, Object.freeze might be the way to go.

[@CodingAqyanoos]

A const is a constant variable And that's correct. The point of const is that you can't create another variable with the same name.

[@Maxim9575]

const always const, don't deceive people!

[@okonkwo.ify18]

First as usual

[@theonlyarjun]

Realised this the hard way, by taking down the prod

[@DaveGrayTeachesCode]

That's the school of hard knocks! Ouch!