5 ms·

> "just make it so I don't have to do crazy checks on properties before casting to a class." You do have 'instanceof' at runtime, so unless you mean some other

> "just make it so I don't have to do crazy checks on properties before casting to a class." You do have 'instanceof' at runtime, so unless you mean some other type of 'class', casting to a class is really a non-issue (and you don't really 'cast'... since dynamic typing and all). If you mean some more advanced concept (e.g., structural type runtime checking), think how you would do it in statically typed languages (is it really better?).

bioemerl 3y ago
Instance of doesn't work sometimes and you have to write explicit property checks. I forget the details because I'm by no means a typescript expert, but I remember being very frustrated by the fact I couldn't just use instance of.
- masklinn 3y ago
  It doesn't work when objects cross global scope boundary (e.g. you get an object from a frame), there's no fixing that, by design the namespaces are different and unrelated.
  - deleted 3y ago
    [deleted]
- lacerrr 3y ago
  instanceof only works with JavaScript classes. Not on regular objects that just structurally conform to a type or interface.
- deleted 3y ago
  [deleted]
likeclockwork 3y ago
Classes aren't the only way to define types?
- amitport 3y ago
  Structural typing is a thing.. also there aren't really classes in js in the Java sense, it's all prototype chains.
  - likeclockwork 3y ago
    instanceof only works for inherited types, usually expressed with the class keyword by TypeScript users. It's entirely worthless if you're not using them. Class is the only construct in TS that is both a type and a value.
- randomdata 3y ago
  JavaScript has half decent object construction syntax that avoids the nesting hell of classes: function Foo(s) { this.s = s } Foo.prototype.bar = function() { console.log(this.s) } const baz = new Foo("Baz") baz.bar() But it seems Typescript can't handle it?
  - amitport 3y ago
    Well there are 2 issues: (1) imperative style mutation of the prototype is runtime dependent, and typescript can't really rely on runtime behavior. (2) Foo has two incompatible types in JS, it is both `(s) => void` and `new (s) => Foo`, typescript by default will assume the first signature (which is usually what people want). In any case, you can specify the types (though in 99% of the cases, just use a class): interface Foo { s: string; bar(): void; } const Foo = function(this: Foo, s: string) { this.s = s; } as { new (s: string): Foo; (this: Foo, s: string): void; }; Foo.prototype.bar = function(this: Foo) { console.log(this.s); } const baz = new Foo('Hello'); baz.bar()
    - randomdata 3y ago
      > though in 99% of the cases, just use a class While that is a fair statement, I've been reading a lot of Typescript code lately and it seems in 99% of cases the selected solution is to use top level functions and globals to avoid the nesting hell class introduces, albeit introducing the global hell in the process. In practice, 'just use a class' doesn't overcome the human element. Javascript was on the right track originally, but then veered off into the weeds for some reason. I appreciate you pointing out how it can be done. Although the solution is very much second class citizen, sadly. This certainly isn't going to wean developers away from global hell. Hopefully Javascript/Typescript can make some strides in improving this going forward.

bioemerl 3y ago

Instance of doesn't work sometimes and you have to write explicit property checks. I forget the details because I'm by no means a typescript expert, but I remember being very frustrated by the fact I couldn't just use instance of.

masklinn 3y ago
It doesn't work when objects cross global scope boundary (e.g. you get an object from a frame), there's no fixing that, by design the namespaces are different and unrelated.
- deleted 3y ago
  [deleted]
lacerrr 3y ago
instanceof only works with JavaScript classes. Not on regular objects that just structurally conform to a type or interface.
deleted 3y ago
[deleted]

likeclockwork 3y ago

Classes aren't the only way to define types?

amitport 3y ago
Structural typing is a thing.. also there aren't really classes in js in the Java sense, it's all prototype chains.
- likeclockwork 3y ago
  instanceof only works for inherited types, usually expressed with the class keyword by TypeScript users. It's entirely worthless if you're not using them. Class is the only construct in TS that is both a type and a value.
randomdata 3y ago
JavaScript has half decent object construction syntax that avoids the nesting hell of classes: function Foo(s) { this.s = s } Foo.prototype.bar = function() { console.log(this.s) } const baz = new Foo("Baz") baz.bar() But it seems Typescript can't handle it?
- amitport 3y ago
  Well there are 2 issues: (1) imperative style mutation of the prototype is runtime dependent, and typescript can't really rely on runtime behavior. (2) Foo has two incompatible types in JS, it is both `(s) => void` and `new (s) => Foo`, typescript by default will assume the first signature (which is usually what people want). In any case, you can specify the types (though in 99% of the cases, just use a class): interface Foo { s: string; bar(): void; } const Foo = function(this: Foo, s: string) { this.s = s; } as { new (s: string): Foo; (this: Foo, s: string): void; }; Foo.prototype.bar = function(this: Foo) { console.log(this.s); } const baz = new Foo('Hello'); baz.bar()
  - randomdata 3y ago
    > though in 99% of the cases, just use a class While that is a fair statement, I've been reading a lot of Typescript code lately and it seems in 99% of cases the selected solution is to use top level functions and globals to avoid the nesting hell class introduces, albeit introducing the global hell in the process. In practice, 'just use a class' doesn't overcome the human element. Javascript was on the right track originally, but then veered off into the weeds for some reason. I appreciate you pointing out how it can be done. Although the solution is very much second class citizen, sadly. This certainly isn't going to wean developers away from global hell. Hopefully Javascript/Typescript can make some strides in improving this going forward.