11–20 of 217 posts
The second example confuses me. The Person type has isCool: boolean, not an explicit true. How does using satisfies here pass coolPeopleOnly?
> TypeScript is a wonderfully advanced language though it has an unfortunately steep learning curve An extremely steep one. The average multi-year TypeScript developer I meet can barely write a basic utility type, let alone has any general (non TypeScript related) notion of cardinality or sub typing. Hell, ask someone to write a signature for array flat, you'd be surprised how many would fail. Too many really stop at…
Also you can so easily go overboard with TS and design all sorts of crazy types and abstractions based on those types that become a net negative in your codebase.
However it does feel really damn nice to have it catch errors and give you great autocomplete and refactoring tooling.
This is wordier than just "as const", what advantage does it give? (I am a newbie and genuinely don't know) edit: perhaps the advantage only comes into play for mutable values, where you want a narrower type than default, but not that narrow. Indeed, this is covered in the article, but CTRL+F "as const" doesn't work on the page for whatever reason, so I missed it.
I’m so frustrated by satisfies because it eliminates optional properties. I want an object of ‘LayerConfig’ elements where each key is the name of a possible layer. Without ‘satisfies’ I have to name every layer twice in my config. But with it, I can’t have optional properties (eg. Half the layers are fine with the default values for some properties). The best I’ve found is a hack that uses a function. But this whole…
> TypeScript is a wonderfully advanced language though it has an unfortunately steep learning curve An extremely steep one. The average multi-year TypeScript developer I meet can barely write a basic utility type, let alone has any general (non TypeScript related) notion of cardinality or sub typing. Hell, ask someone to write a signature for array flat, you'd be surprised how many would fail. Too many really stop at…
I don’t think that means it has a steep learning curve. It just means the basics suffice for a ton of TypeScript deployments. Which I personally don’t see as the end of the world.
This is wordier than just "as const", what advantage does it give? (I am a newbie and genuinely don't know) edit: perhaps the advantage only comes into play for mutable values, where you want a narrower type than default, but not that narrow. Indeed, this is covered in the article, but CTRL+F "as const" doesn't work on the page for whatever reason, so I missed it.
This is wordier than just "as const", what advantage does it give? (I am a newbie and genuinely don't know) edit: perhaps the advantage only comes into play for mutable values, where you want a narrower type than default, but not that narrow. Indeed, this is covered in the article, but CTRL+F "as const" doesn't work on the page for whatever reason, so I missed it.
1. Enforce that a value adheres to a specific type
2. But, doesn't cause the value to be cast to that type.
For example, if you have a Rect type like:
type Rect = { w: number, h: number }
const a = { x: 0, y: 0, w: 5, h: 5 };
const a: Rect = // ...
as Rect
type Location = { x: number, y: number };
const a: Location & Rect = // ...
The satisfies keyword does what you want in this case: it enforces the object conforms to the type, without casting it to the type.
const a = { x: 0, y: 0, w: 5, h: 5 } satisfies Rect;
// a.x works
const a = { x: 0, y: 0, width: 5, height: 5 } satisfies Rect;
> TypeScript is a wonderfully advanced language though it has an unfortunately steep learning curve An extremely steep one. The average multi-year TypeScript developer I meet can barely write a basic utility type, let alone has any general (non TypeScript related) notion of cardinality or sub typing. Hell, ask someone to write a signature for array flat, you'd be surprised how many would fail. Too many really stop at…
Honestly I just use TypeScript to prevent `1 + [] == "1"` and check that functions are called with arguments. I don't care about type theory at all and the whole thing strikes me as programmers larping (poorly) as mathematicians.
If you type some state as:
isLoading: boolean
result: Foo
hasError: boolean
errorMessage: string | null
And that is a very simple and basic example, you can go *much* further, as in encoding that some type isn't merely a number through branded types, but a special type of number, be it a positive number between 2 and 200 or, being $ or celsius and avoiding again and entire class of bugs by treating everybody just as an integer or float.
> TypeScript is a wonderfully advanced language though it has an unfortunately steep learning curve An extremely steep one. The average multi-year TypeScript developer I meet can barely write a basic utility type, let alone has any general (non TypeScript related) notion of cardinality or sub typing. Hell, ask someone to write a signature for array flat, you'd be surprised how many would fail. Too many really stop at…
> Too many really stop at the very basics. I don’t think that means it has a steep learning curve. It just means the basics suffice for a ton of TypeScript deployments. Which I personally don’t see as the end of the world.
While I aspire to Library TS levels of skill, I am really only a bit past App TS myself.
On that note I've been meaning to the the Type-Level Typescript course [0]. Has anyone taken it?
This is wordier than just "as const", what advantage does it give? (I am a newbie and genuinely don't know) edit: perhaps the advantage only comes into play for mutable values, where you want a narrower type than default, but not that narrow. Indeed, this is covered in the article, but CTRL+F "as const" doesn't work on the page for whatever reason, so I missed it.
The satisfies keyword is quite different than "as const." What it does is: 1. Enforce that a value adheres to a specific type 2. But, doesn't cause the value to be cast to that type. For example, if you have a Rect type like: type Rect = { w: number, h: number } You might want to enforce that some value satisfies Rect properties... But also allow it to have others. For example: const a = { x: 0, y: 0, w: 5, h: 5 }; I…