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That's what I thought, so you're telling me those validation types silently fail at runtime (so in most cases)? This is insane

throw_m239339 6y ago
> This is insane No, Typescript is very much just a static code analysis tool for JavaScript, there is no runtime at all, and there should not be one. It confuses a lot of people because they expect type guards at runtime, but it was never in the scope of the language to provide something like that.
- debaserab2 6y ago
  And, to be honest, for the vast majority that are new to type systems it's probably OK and very likely one of the reasons for TypeScripts rapid adoption. In my experience it really is the case that some typing is better than none at all.
__ryan__ 6y ago
TypeScript checks that the types are correct at compile time. If you are strict, don’t intentionally try to outsmart the type system, and use manual runtime type checking when necessary [0], TypeScript does a good practical job of ensuring that you won’t run into runtime type errors. The reason TypeScript doesn’t automatically include runtime type information is (probably) because the overhead of runtime type checking would outweigh the benefit when static type checking does a good enough job. Also, JavaScript being a dynamic language has allowed some pretty complex patterns of types to emerge from real-world use cases that would be exhausting to enforce all the time at runtime. Typically in TypeScript, runtime type checking is (manually) done when the type system cannot otherwise confidently guarantee the type of a value. For example, it’s common to have a runtime check for the shape of a JSON api response because you’re not necessarily in control of what that will actually return. There are community supported packages to help make this easier [1]. 0: https://www.typescriptlang.org/docs/handbook/advanced-types.html https://www.typescriptlang.org/docs/handbook/advanced-types.... 1: https://github.com/gcanti/io-ts https://github.com/gcanti/io-ts

throw_m239339 6y ago

> This is insane No, Typescript is very much just a static code analysis tool for JavaScript, there is no runtime at all, and there should not be one. It confuses a lot of people because they expect type guards at runtime, but it was never in the scope of the language to provide something like that.

debaserab2 6y ago
And, to be honest, for the vast majority that are new to type systems it's probably OK and very likely one of the reasons for TypeScripts rapid adoption. In my experience it really is the case that some typing is better than none at all.

__ryan__ 6y ago

TypeScript checks that the types are correct at compile time. If you are strict, don’t intentionally try to outsmart the type system, and use manual runtime type checking when necessary [0], TypeScript does a good practical job of ensuring that you won’t run into runtime type errors. The reason TypeScript doesn’t automatically include runtime type information is (probably) because the overhead of runtime type checking would outweigh the benefit when static type checking does a good enough job. Also, JavaScript being a dynamic language has allowed some pretty complex patterns of types to emerge from real-world use cases that would be exhausting to enforce all the time at runtime. Typically in TypeScript, runtime type checking is (manually) done when the type system cannot otherwise confidently guarantee the type of a value. For example, it’s common to have a runtime check for the shape of a JSON api response because you’re not necessarily in control of what that will actually return. There are community supported packages to help make this easier [1]. 0: https://www.typescriptlang.org/docs/handbook/advanced-types.html https://www.typescriptlang.org/docs/handbook/advanced-types.... 1: https://github.com/gcanti/io-ts https://github.com/gcanti/io-ts